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Cochrane Database of Systematic Reviews

Vaccines for preventing influenza in the elderly

Information

DOI:
https://doi.org/10.1002/14651858.CD004876.pub4Copy DOI
Database:
  1. Cochrane Database of Systematic Reviews
Version published:
  1. 01 February 2018see what's new
Type:
  1. Intervention
Stage:
  1. Review
Cochrane Editorial Group:
  1. Cochrane Acute Respiratory Infections Group

Copyright:
  1. Copyright © 2018 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

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Authors

  • Vittorio Demicheli

    Correspondence to: Italy

    [email protected]

  • Tom Jefferson

    Department of Continuing Education, University of Oxford, Oxford, Italy

  • Carlo Di Pietrantonj

    Regional Epidemiology Unit SeREMI, Local Health Unit Alessandria- ASL AL, Alessandria, Italy

  • Eliana Ferroni

    Epidemiological System of the Veneto Region, Regional Center for Epidemiology, Veneto Region, Padova, Italy

  • Sarah Thorning

    GCUH Library, Gold Coast Hospital and Health Service, Southport, Australia

  • Roger E Thomas

    Department of Family Medicine, Faculty of Medicine, University of Calgary, Calgary, Canada

  • Alessandro Rivetti

    S.S.D. Epidemiologia - Dipartimento di Prevenzione, ASL CN2 Alba Bra, Alba, Italy

Contributions of authors

Alessandro Rivetti conducted the original searches.
Tom Jefferson, Daniela Rivetti, and Vittorio Demicheli applied inclusion criteria.
Tom Jefferson, Daniela Rivetti, and Melanie Rudin extracted the original data.
Vittorio Demicheli arbitrated and checked the data extraction.
Carlo Di Pietrantonj undertook the meta‐analysis and performed statistical testing.
Tom Jefferson wrote the first review and the updates.
Eliana Ferroni extracted the data.
For the 2016 update, Sarah Thorning conducted the updated searches, Tom Jefferson and Alessandro Rivetti wrote the review, Vittorio Demicheli checked the data, and all authors contributed to the final updated review.

Sources of support

Internal sources

  • ASL 20 (Alessandria), ASL 19 (Asti), Regione Piemonte, Italy

External sources

  • National Health and Medical Research Council (NHMRC), Australia

Declarations of interest

Vittorio Demicheli: none known.

Tom Jefferson (TJ) was a recipient of a UK National Institute for Health Research grant for a Cochrane Review of neuraminidase inhibitors for influenza. In addition, TJ receives royalties from his books published by Il Pensiero Scientifico Editore, Rome and Blackwells. TJ is occasionally interviewed by market research companies about phase I or II pharmaceutical products (remunerated). In 2011‐13, TJ acted as an expert witness in litigation related to the antiviral oseltamivir, in two litigation cases on potential vaccine‐related damage, and in a labour case on influenza vaccines in healthcare workers in Canada (remunerated). He has acted as a consultant for Roche (1997‐99), GSK (2001‐2), Sanofi‐Synthelabo (2003), and IMS Health (2013) (remunerated). In 2014 he was retained as a scientific adviser to a legal team acting on oseltamivir (remunerated). TJ has a potential financial conflict of interest in the drug oseltamivir. In 2014‐16, TJ was a member of three advisory boards for Boerhinger Ingelheim (remunerated). TJ is holder of a Cochrane Methods Innovations Fund grant to develop guidance on the use of regulatory data in Cochrane Reviews. TJ was a member of an independent data monitoring committee for a Sanofi Pasteur clinical trial on an influenza vaccine (remunerated). Between 1994 and 2013, TJ was the co‐ordinator of the Cochrane Vaccines Field. TJ is a cosignatory of the Nordic Cochrane Centre Complaint to the European Medicines Agency (EMA) over maladministration at the EMA in relation to the investigation of alleged harms of human papillomavirus vaccines and consequent complaints to the European Ombudsman. TJ is coholder of a John and Laura Arnold Foundation grant for development of a RIAT support centre (2017‐20) and Jean Monnet Network Grant, 2017‐20 for The Jean Monnet Health Law and Policy Network.

Carlo Di Pietrantonj: none known.

Eliana Ferroni: none known.

Sarah Thorning: none known.

Roger E Thomas: none known.

Alessandro Rivetti: none known.

Acknowledgements

The 2016 update was funded by the Cochrane Review Support Programme.

The review authors wish to acknowledge Daniela Rivetti, Melanie Rudin and Lubna Al‐Ansary as previous authors.

The authors gratefully acknowledge the following people for commenting on previous drafts: Amy Zelmer, Laila Tata, Lohne Simonsen, Sree Nair Maryann Napoli, Anne Lyddiat, Wendy Keitel, Ludovic Reveiz, Mark Jones, Chris Del Mar and Geoff Spurling.

For this 2016 update, we acknowledge help and comments received from Liz Dooley, Toby Lasserson, David Honeyman, Janet Wale, Soumyadeep Bhaumik, Mark Jones, and Jenny Doust. We thank Lisa Winer for copy‐editing this update.

Version history

Published

Title

Stage

Authors

Version

2018 Feb 01

Vaccines for preventing influenza in the elderly

Review

Vittorio Demicheli, Tom Jefferson, Carlo Di Pietrantonj, Eliana Ferroni, Sarah Thorning, Roger E Thomas, Alessandro Rivetti

https://doi.org/10.1002/14651858.CD004876.pub4

2010 Feb 17

Vaccines for preventing influenza in the elderly

Review

Tom Jefferson, Carlo Di Pietrantonj, Lubna A Al‐Ansary, Eliana Ferroni, Sarah Thorning, Roger E Thomas

https://doi.org/10.1002/14651858.CD004876.pub3

2006 Jul 19

Vaccines for preventing influenza in the elderly

Review

Daniela Rivetti, Tom Jefferson, Roger E Thomas, Melanie Rudin, Alessandro Rivetti, Carlo Di Pietrantonj, Vittorio Demicheli

https://doi.org/10.1002/14651858.CD004876.pub2

2005 Jan 24

Vaccines for preventing influenza in the elderly

Protocol

Daniela Rivetti, Vittorio Demicheli, Carlo Di Pietrantonj, Tom Jefferson, Roger E Thomas

https://doi.org/10.1002/14651858.CD004876

Differences between protocol and review

Prior to starting the 2016 update of this review, we decided that evidence from observational studies should no longer be updated, given its inherent biases and our intention to focus the main synthesis, 'Summary of findings' tables, conclusions, and summary versions on randomised evidence. For historical purposes we have retained data from non‐randomised evidence in the review.

In previous versions of this review, we computed the reciprocal of the pooled risk difference as the basis for calculating numbers needed to vaccinate (NNV). Given expected variation in control group risks, we decided to revise this approach and have calculated NNVs based on the difference between the assumed and corresponding risks based on the summary of findings Table 1.

Keywords

MeSH

PICOs

Population
Intervention
Comparison
Outcome

The PICO model is widely used and taught in evidence-based health care as a strategy for formulating questions and search strategies and for characterizing clinical studies or meta-analyses. PICO stands for four different potential components of a clinical question: Patient, Population or Problem; Intervention; Comparison; Outcome.

See more on using PICO in the Cochrane Handbook.

Study flow. We identified no new randomised controlled trials for the 2016 update and stabilisation.

Figures and Tables -
Figure 1

Study flow. We identified no new randomised controlled trials for the 2016 update and stabilisation.

Relationship between vaccination rate and attack rate

Figures and Tables -
Figure 2

Relationship between vaccination rate and attack rate

Comparison 1: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine, Outcome 1: Influenza

Figures and Tables -
Analysis 1.1

Comparison 1: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine, Outcome 1: Influenza

Comparison 1: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine, Outcome 2: Influenza‐like illness

Figures and Tables -
Analysis 1.2

Comparison 1: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine, Outcome 2: Influenza‐like illness

Comparison 1: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine, Outcome 3: Pneumonia

Figures and Tables -
Analysis 1.3

Comparison 1: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine, Outcome 3: Pneumonia

Comparison 1: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine, Outcome 4: All deaths

Figures and Tables -
Analysis 1.4

Comparison 1: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine, Outcome 4: All deaths

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 1: General malaise

Figures and Tables -
Analysis 2.1

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 1: General malaise

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 2: Nausea

Figures and Tables -
Analysis 2.2

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 2: Nausea

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 3: Upper respiratory tract symptoms

Figures and Tables -
Analysis 2.3

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 3: Upper respiratory tract symptoms

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 4: Headache

Figures and Tables -
Analysis 2.4

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 4: Headache

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 5: Fever

Figures and Tables -
Analysis 2.5

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 5: Fever

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 6: Local tenderness/sore arm

Figures and Tables -
Analysis 2.6

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 6: Local tenderness/sore arm

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 7: Swelling ‐ erythema ‐ induration

Figures and Tables -
Analysis 2.7

Comparison 2: Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events, Outcome 7: Swelling ‐ erythema ‐ induration

Comparison 3: Influenza vaccines versus placebo: randomised controlled trials ‐ inactivated aerosol vaccine, Outcome 1: Influenza

Figures and Tables -
Analysis 3.1

Comparison 3: Influenza vaccines versus placebo: randomised controlled trials ‐ inactivated aerosol vaccine, Outcome 1: Influenza

Comparison 3: Influenza vaccines versus placebo: randomised controlled trials ‐ inactivated aerosol vaccine, Outcome 2: Influenza‐like illness

Figures and Tables -
Analysis 3.2

Comparison 3: Influenza vaccines versus placebo: randomised controlled trials ‐ inactivated aerosol vaccine, Outcome 2: Influenza‐like illness

Comparison 4: Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine, Outcome 1: Influenza

Figures and Tables -
Analysis 4.1

Comparison 4: Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine, Outcome 1: Influenza

Comparison 5: Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine ‐ adverse events, Outcome 1: General malaise

Figures and Tables -
Analysis 5.1

Comparison 5: Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine ‐ adverse events, Outcome 1: General malaise

Comparison 5: Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine ‐ adverse events, Outcome 2: Fever

Figures and Tables -
Analysis 5.2

Comparison 5: Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine ‐ adverse events, Outcome 2: Fever

Comparison 5: Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine ‐ adverse events, Outcome 3: Upper respiratory tract symptoms

Figures and Tables -
Analysis 5.3

Comparison 5: Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine ‐ adverse events, Outcome 3: Upper respiratory tract symptoms

Comparison 5: Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine ‐ adverse events, Outcome 4: Lower respiratory tract symptoms

Figures and Tables -
Analysis 5.4

Comparison 5: Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine ‐ adverse events, Outcome 4: Lower respiratory tract symptoms

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 1: Influenza

Figures and Tables -
Analysis 6.1

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 1: Influenza

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 2: Influenza‐like illness

Figures and Tables -
Analysis 6.2

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 2: Influenza‐like illness

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 3: Pneumonia

Figures and Tables -
Analysis 6.3

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 3: Pneumonia

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 4: Hospitalisation for influenza‐like illness or pneumonia

Figures and Tables -
Analysis 6.4

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 4: Hospitalisation for influenza‐like illness or pneumonia

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 5: Deaths from flu or pneumonia

Figures and Tables -
Analysis 6.5

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 5: Deaths from flu or pneumonia

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 6: All deaths

Figures and Tables -
Analysis 6.6

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 6: All deaths

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 7: Influenza cases (clinically defined without clear definition)

Figures and Tables -
Analysis 6.7

Comparison 6: Influenza vaccines versus no vaccination: cohort studies in nursing homes, Outcome 7: Influenza cases (clinically defined without clear definition)

Comparison 7: Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in nursing homes, Outcome 1: Influenza‐like illness

Figures and Tables -
Analysis 7.1

Comparison 7: Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in nursing homes, Outcome 1: Influenza‐like illness

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 1: Influenza

Figures and Tables -
Analysis 8.1

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 1: Influenza

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 2: Influenza‐like illness

Figures and Tables -
Analysis 8.2

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 2: Influenza‐like illness

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 3: Pneumonia

Figures and Tables -
Analysis 8.3

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 3: Pneumonia

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 4: Hospitalisation for flu or pneumonia

Figures and Tables -
Analysis 8.4

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 4: Hospitalisation for flu or pneumonia

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 5: Hospitalisation for any respiratory disease

Figures and Tables -
Analysis 8.5

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 5: Hospitalisation for any respiratory disease

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 6: Deaths from flu or pneumonia

Figures and Tables -
Analysis 8.6

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 6: Deaths from flu or pneumonia

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 7: Deaths from respiratory disease

Figures and Tables -
Analysis 8.7

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 7: Deaths from respiratory disease

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 8: All deaths

Figures and Tables -
Analysis 8.8

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 8: All deaths

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 9: Hospitalisation for heart disease

Figures and Tables -
Analysis 8.9

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 9: Hospitalisation for heart disease

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 10: Combined outcome: all deaths or severe respiratory illness

Figures and Tables -
Analysis 8.10

Comparison 8: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 10: Combined outcome: all deaths or severe respiratory illness

Comparison 9: Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates, Outcome 1: Hospitalisation for influenza or pneumonia

Figures and Tables -
Analysis 9.1

Comparison 9: Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates, Outcome 1: Hospitalisation for influenza or pneumonia

Comparison 9: Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates, Outcome 2: Hospitalisation for any respiratory disease

Figures and Tables -
Analysis 9.2

Comparison 9: Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates, Outcome 2: Hospitalisation for any respiratory disease

Comparison 9: Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates, Outcome 3: Hospitalisation for heart disease

Figures and Tables -
Analysis 9.3

Comparison 9: Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates, Outcome 3: Hospitalisation for heart disease

Comparison 9: Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates, Outcome 4: All deaths

Figures and Tables -
Analysis 9.4

Comparison 9: Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates, Outcome 4: All deaths

Comparison 9: Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates, Outcome 5: Combined outcome: all deaths or severe respiratory illness

Figures and Tables -
Analysis 9.5

Comparison 9: Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates, Outcome 5: Combined outcome: all deaths or severe respiratory illness

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 1: Influenza

Figures and Tables -
Analysis 10.1

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 1: Influenza

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 2: Pneumonia

Figures and Tables -
Analysis 10.2

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 2: Pneumonia

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 3: Hospitalisation for influenza or pneumonia

Figures and Tables -
Analysis 10.3

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 3: Hospitalisation for influenza or pneumonia

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 4: Hospitalisation for any respiratory disease

Figures and Tables -
Analysis 10.4

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 4: Hospitalisation for any respiratory disease

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 5: Deaths from respiratory disease

Figures and Tables -
Analysis 10.5

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 5: Deaths from respiratory disease

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 6: All deaths

Figures and Tables -
Analysis 10.6

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 6: All deaths

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 7: Hospitalisation for heart disease

Figures and Tables -
Analysis 10.7

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 7: Hospitalisation for heart disease

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 8: Combined outcome: all deaths or severe respiratory illness

Figures and Tables -
Analysis 10.8

Comparison 10: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups, Outcome 8: Combined outcome: all deaths or severe respiratory illness

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 1: Influenza

Figures and Tables -
Analysis 11.1

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 1: Influenza

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 2: Pneumonia

Figures and Tables -
Analysis 11.2

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 2: Pneumonia

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 3: Hospitalisation for influenza or pneumonia

Figures and Tables -
Analysis 11.3

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 3: Hospitalisation for influenza or pneumonia

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 4: Hospitalisation for any respiratory disease

Figures and Tables -
Analysis 11.4

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 4: Hospitalisation for any respiratory disease

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 5: Deaths from respiratory disease

Figures and Tables -
Analysis 11.5

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 5: Deaths from respiratory disease

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 6: All deaths

Figures and Tables -
Analysis 11.6

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 6: All deaths

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 7: Hospitalisation for heart disease

Figures and Tables -
Analysis 11.7

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 7: Hospitalisation for heart disease

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 8: Combined outcome: all deaths or severe respiratory illness

Figures and Tables -
Analysis 11.8

Comparison 11: Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups, Outcome 8: Combined outcome: all deaths or severe respiratory illness

Comparison 12: Influenza and pneumococcal vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 1: Influenza‐like illness

Figures and Tables -
Analysis 12.1

Comparison 12: Influenza and pneumococcal vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 1: Influenza‐like illness

Comparison 12: Influenza and pneumococcal vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 2: Hospitalisation for influenza or pneumonia or respiratory disease

Figures and Tables -
Analysis 12.2

Comparison 12: Influenza and pneumococcal vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 2: Hospitalisation for influenza or pneumonia or respiratory disease

Comparison 12: Influenza and pneumococcal vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 3: Deaths from influenza or pneumonia

Figures and Tables -
Analysis 12.3

Comparison 12: Influenza and pneumococcal vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 3: Deaths from influenza or pneumonia

Comparison 12: Influenza and pneumococcal vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 4: All deaths

Figures and Tables -
Analysis 12.4

Comparison 12: Influenza and pneumococcal vaccines versus no vaccination: cohort studies in community‐dwellers, Outcome 4: All deaths

Comparison 13: Influenza vaccines with adjuvant versus no vaccination: cohort studies in community‐dwellers, Outcome 1: Influenza‐like illness

Figures and Tables -
Analysis 13.1

Comparison 13: Influenza vaccines with adjuvant versus no vaccination: cohort studies in community‐dwellers, Outcome 1: Influenza‐like illness

Comparison 13: Influenza vaccines with adjuvant versus no vaccination: cohort studies in community‐dwellers, Outcome 2: Hospitalisation for influenza or pneumonia or respiratory disease

Figures and Tables -
Analysis 13.2

Comparison 13: Influenza vaccines with adjuvant versus no vaccination: cohort studies in community‐dwellers, Outcome 2: Hospitalisation for influenza or pneumonia or respiratory disease

Comparison 13: Influenza vaccines with adjuvant versus no vaccination: cohort studies in community‐dwellers, Outcome 3: All deaths

Figures and Tables -
Analysis 13.3

Comparison 13: Influenza vaccines with adjuvant versus no vaccination: cohort studies in community‐dwellers, Outcome 3: All deaths

Comparison 14: Influenza vaccines versus no vaccination: case‐control studies in community, Outcome 1: Hospitalisations for influenza or pneumonia

Figures and Tables -
Analysis 14.1

Comparison 14: Influenza vaccines versus no vaccination: case‐control studies in community, Outcome 1: Hospitalisations for influenza or pneumonia

Comparison 14: Influenza vaccines versus no vaccination: case‐control studies in community, Outcome 2: Hospitalisations for any respiratory disease

Figures and Tables -
Analysis 14.2

Comparison 14: Influenza vaccines versus no vaccination: case‐control studies in community, Outcome 2: Hospitalisations for any respiratory disease

Comparison 14: Influenza vaccines versus no vaccination: case‐control studies in community, Outcome 3: Deaths from influenza or pneumonia

Figures and Tables -
Analysis 14.3

Comparison 14: Influenza vaccines versus no vaccination: case‐control studies in community, Outcome 3: Deaths from influenza or pneumonia

Comparison 14: Influenza vaccines versus no vaccination: case‐control studies in community, Outcome 4: Pneumonia (no better defined)

Figures and Tables -
Analysis 14.4

Comparison 14: Influenza vaccines versus no vaccination: case‐control studies in community, Outcome 4: Pneumonia (no better defined)

Comparison 15: Influenza vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates, Outcome 1: Hospitalisations for influenza or pneumonia

Figures and Tables -
Analysis 15.1

Comparison 15: Influenza vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates, Outcome 1: Hospitalisations for influenza or pneumonia

Comparison 15: Influenza vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates, Outcome 2: Hospitalisations for any respiratory disease

Figures and Tables -
Analysis 15.2

Comparison 15: Influenza vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates, Outcome 2: Hospitalisations for any respiratory disease

Comparison 15: Influenza vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates, Outcome 3: Deaths from pneumonia or influenza

Figures and Tables -
Analysis 15.3

Comparison 15: Influenza vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates, Outcome 3: Deaths from pneumonia or influenza

Comparison 16: Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in community, Outcome 1: Hospitalisations for influenza or pneumonia

Figures and Tables -
Analysis 16.1

Comparison 16: Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in community, Outcome 1: Hospitalisations for influenza or pneumonia

Comparison 17: Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates, Outcome 1: Hospitalisations for influenza or pneumonia

Figures and Tables -
Analysis 17.1

Comparison 17: Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates, Outcome 1: Hospitalisations for influenza or pneumonia

Comparison 18: Sensitivity analysis: comparison 01: subgroup analysis by study quality, Outcome 1: Influenza‐like illness

Figures and Tables -
Analysis 18.1

Comparison 18: Sensitivity analysis: comparison 01: subgroup analysis by study quality, Outcome 1: Influenza‐like illness

Summary of findings 1. Influenza vaccine compared to placebo for preventing influenza in the elderly

Influenza vaccine compared to placebo for preventing influenza in the elderly

Patient or population: people aged over 65 years
Setting: community and residential care institutions in the USA and Europe during influenza seasons between 1965 and 2000
Intervention: influenza vaccine
Comparison: placebo

Outcomes

Anticipated absolute effects* (95% CI)

Relative effect
(95% CI)

№ of participants
(studies)

Quality of the evidence
(GRADE)

Comments

Risk with placebo

Risk with influenza vaccine

Influenza assessed with: laboratory confirmation

Follow‐up was conducted over an influenza season.

Study population1

RR 0.42
(0.27 to 0.66)

2217
(3 RCTs)

⊕⊕⊝⊝
LOW 2 3

57 per 1000

24 per 1000
(15 to 38)

Influenza‐like illness
assessed with: subjective report

Follow‐up was conducted over an influenza season.

Study population1

RR 0.59
(0.47 to 0.73)

6894
(4 RCTs)

⊕⊕⊕⊝
MODERATE 2

59 per 1000

35 per 1000
(28 to 43)

Pneumonia

Follow‐up was conducted over an influenza season.

No events occurred in 1 study of 699 people.

699
(1 RCT)

⊕⊝⊝⊝
VERY LOW 4 5

Hospitalisations ‐ not reported

All deaths

Follow‐up was conducted over an influenza season.

Study population1

RR 1.02
(0.11 to 9.72)

699
(1 RCT)

⊕⊝⊝⊝
VERY LOW 4 5

6 per 1000

6 per 1000
(1 to 55)

Fever

Follow‐up was conducted over an influenza season.

Study population1

RR 1.57
(0.92 to 2.71)

2519
(3 RCTs)

⊕⊕⊕⊝
MODERATE 6

16 per 1000

25 per 1000
(15 to 43)

Nausea

Follow‐up was conducted over an influenza season.

Study population1

RR 1.75
(0.74 to 4.12)

672
(1 RCT)

⊕⊕⊝⊝
LOW 6 7

24 per 1000

42 per 1000
(18 to 98)

*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: confidence interval; RCT: randomised controlled trial; RR: risk ratio

GRADE Working Group grades of evidence
High quality: We are very confident that the true effect lies close to that of the estimate of the effect.
Moderate quality: We are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.
Low quality: Our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect.
Very low quality: We have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.

1Control group risk taken as aggregate of the study control group risks.
2Downgraded one level due to serious risk of bias. Most of the evidence summarised in the meta‐analysis comes from studies with high or unclear risk of bias for more than one 'Risk of bias' domain.
3Downgraded due to indirectness. Uncertainty over the definition, testing, and surveillance of influenza in older trials.
4Downgraded two levels due to very serious imprecision. No events occurred in one study of nearly 700 people. The study was likely underpowered to detect effects on either pneumonia or mortality.
5Downgraded one level due to serious risk of bias. One study contributing data to this outcome had high risk of selection bias.
6Downgraded one level due to serious imprecision. Confidence intervals for nausea and fever were wide and include reduction and increase in risk of adverse events.
7Downgraded one level due to serious risk of bias. One study contributing data to this outcome had unclear risk of selection bias.

Figures and Tables -
Summary of findings 1. Influenza vaccine compared to placebo for preventing influenza in the elderly
Table 1. Studies included in the various versions of this review and their impact on our conclusions

Review version (searches date)

Number of included trials (RCTs/CCTs)

Number of included observational studies

Estimates of effect (RCTs/CCTs only)

Conclusions (1 to 2 lines from abstract)

Version 1

(24 May 2006)

9

621

Influenza‐like illness

LAIV = no data

TIV = 41% (95% CI 27% to 53%)

IAV = n.s.

Influenza

LAIV = n.s.

TIV = 58% (95% CI 34% to 73%)

IAV = n.s.

In long‐term care facilities, where vaccination is most effective against complications, the aims of the vaccination campaign are fulfilled, at least in part. However, according to reliable evidence the usefulness of vaccines in the community is modest.

The apparent high effectiveness of the vaccines in preventing death from all causes may reflect a baseline imbalance in health status and other systematic differences in the 2 groups of participants.

Version 2

(20 January 2010)

9

662

Influenza‐like illness

LAIV = no data

TIV = 41% (95% CI 27% to 53%)

IAV = n.s.

Influenza

LAIV = n.s.

TIV = 58% (95% CI 34% to 73%)

IAV = n.s.

The available evidence is of poor quality and provides no guidance regarding the safety, efficacy, or effectiveness of influenza vaccines for people aged 65 years or older. To resolve the uncertainty, an adequately powered publicly‐funded randomised, placebo‐controlled trial run over several seasons should be undertaken.

1These include 49 cohort studies for efficacy/effectiveness (79 data sets); 10 case‐control studies for efficacy/effectiveness (12 data sets); 3 studies (cohorts) for Guillain‐Barré syndrome.
2For this update, two cohort studies and two case‐control studies were added to the review (all assessing efficacy/effectiveness).

Key: CCT = controlled clinical trial; CI = confidence interval; IAV = inactivated aerosol vaccines; LAIV = live attenuated vaccines; n.s. = not significant; RCT = randomised controlled trial; TIV = trivalent inactivated vaccines

Figures and Tables -
Table 1. Studies included in the various versions of this review and their impact on our conclusions
Table 2. Guillain‐Barré syndrome

Study

Influenza season

Vaccine

Population

Age

RR (95% CI)

Schonberger 1979

1976 to 1977

A/New Jersey/76 or A/New Jersey/76 and A/Victoria/75 swine vaccine

All the USA population

> 64 years

5.2 (3.9 to 7.0)

Kaplan 1982

1979 to 1980

Inactivated trivalent

All the USA population

> 18 years

0.6 (0.45 to 1.32)

Kaplan 1982

1980 to 1981

Inactivated trivalent

All the USA population

> 18 years

1.4 (0.80 to 1.76)

Lasky 1998

1992 to 1994

Inactivated trivalent

21 million

> 64 years

1.5 (0.7 to 3.3)

Key: CI = confidence interval; RR = risk ratio

Figures and Tables -
Table 2. Guillain‐Barré syndrome
Comparison 1. Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

1.1 Influenza Show forest plot

3

2217

Risk Ratio (M‐H, Random, 95% CI)

0.42 [0.27, 0.66]

1.1.1 Outbreak ‐ vaccine matching ‐ community ‐ healthy and ill

1

1838

Risk Ratio (M‐H, Random, 95% CI)

0.41 [0.23, 0.74]

1.1.2 Outbreak ‐ vaccine matching ‐ psychiatric hospital

1

177

Risk Ratio (M‐H, Random, 95% CI)

0.35 [0.12, 1.06]

1.1.3 No outbreak ‐ vaccine matching ‐ nursing home ‐ healthy and ill

1

202

Risk Ratio (M‐H, Random, 95% CI)

0.50 [0.20, 1.25]

1.2 Influenza‐like illness Show forest plot

4

6894

Risk Ratio (M‐H, Random, 95% CI)

0.59 [0.47, 0.73]

1.2.1 Outbreak ‐ vaccine matching (circulating strains) ‐ community ‐ healthy

2

2047

Risk Ratio (M‐H, Random, 95% CI)

0.57 [0.42, 0.79]

1.2.2 Outbreak ‐ vaccine matching ‐ community ‐ risk groups

1

490

Risk Ratio (M‐H, Random, 95% CI)

0.87 [0.49, 1.53]

1.2.3 Outbreak ‐ vaccine matching ‐ nursing home ‐ healthy

1

4180

Risk Ratio (M‐H, Random, 95% CI)

0.54 [0.37, 0.80]

1.2.4 Outbreak ‐ vaccine matching ‐ psychiatric hospital

1

177

Risk Ratio (M‐H, Random, 95% CI)

0.35 [0.13, 0.92]

1.3 Pneumonia Show forest plot

1

Risk Ratio (M‐H, Random, 95% CI)

Totals not selected

1.3.1 Outbreak ‐ vaccine matching ‐ community ‐ healthy

1

Risk Ratio (M‐H, Random, 95% CI)

Totals not selected

1.4 All deaths Show forest plot

1

Risk Ratio (M‐H, Random, 95% CI)

Totals not selected

1.4.1 Outbreak ‐ vaccine matching ‐ community ‐ healthy

1

Risk Ratio (M‐H, Random, 95% CI)

Totals not selected

Figures and Tables -
Comparison 1. Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine
Comparison 2. Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

2.1 General malaise Show forest plot

4

2560

Risk Ratio (M‐H, Random, 95% CI)

1.18 [0.87, 1.61]

2.2 Nausea Show forest plot

1

672

Risk Ratio (M‐H, Random, 95% CI)

1.75 [0.74, 4.12]

2.3 Upper respiratory tract symptoms Show forest plot

2

713

Risk Ratio (M‐H, Random, 95% CI)

1.35 [0.90, 2.01]

2.4 Headache Show forest plot

3

2519

Risk Ratio (M‐H, Random, 95% CI)

1.10 [0.76, 1.58]

2.5 Fever Show forest plot

3

2519

Risk Ratio (M‐H, Random, 95% CI)

1.57 [0.92, 2.71]

2.6 Local tenderness/sore arm Show forest plot

4

2560

Risk Ratio (M‐H, Random, 95% CI)

3.56 [2.61, 4.87]

2.7 Swelling ‐ erythema ‐ induration Show forest plot

2

1847

Risk Ratio (M‐H, Random, 95% CI)

8.23 [3.98, 17.05]

Figures and Tables -
Comparison 2. Influenza vaccines versus placebo: randomised controlled trials ‐ parenteral vaccine ‐ adverse events
Comparison 3. Influenza vaccines versus placebo: randomised controlled trials ‐ inactivated aerosol vaccine

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

3.1 Influenza Show forest plot

1

176

Risk Ratio (M‐H, Random, 95% CI)

0.89 [0.40, 1.99]

3.1.1 Outbreak ‐ vaccine matching ‐ psychiatric hospital

1

176

Risk Ratio (M‐H, Random, 95% CI)

0.89 [0.40, 1.99]

3.2 Influenza‐like illness Show forest plot

1

176

Risk Ratio (M‐H, Random, 95% CI)

0.84 [0.41, 1.71]

3.2.1 Outbreak ‐ vaccine matching ‐ psychiatric hospital

1

176

Risk Ratio (M‐H, Random, 95% CI)

0.84 [0.41, 1.71]

Figures and Tables -
Comparison 3. Influenza vaccines versus placebo: randomised controlled trials ‐ inactivated aerosol vaccine
Comparison 4. Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

4.1 Influenza Show forest plot

1

220

Risk Ratio (M‐H, Random, 95% CI)

0.49 [0.21, 1.17]

4.1.1 No outbreak ‐ vaccine matching ‐ nursing home ‐ healthy and ill

1

220

Risk Ratio (M‐H, Random, 95% CI)

0.49 [0.21, 1.17]

Figures and Tables -
Comparison 4. Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine
Comparison 5. Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine ‐ adverse events

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

5.1 General malaise Show forest plot

1

45

Risk Ratio (M‐H, Random, 95% CI)

3.09 [0.18, 53.20]

5.2 Fever Show forest plot

1

45

Risk Ratio (M‐H, Random, 95% CI)

1.71 [0.09, 33.24]

5.3 Upper respiratory tract symptoms Show forest plot

1

45

Risk Ratio (M‐H, Random, 95% CI)

1.62 [0.42, 6.29]

5.4 Lower respiratory tract symptoms Show forest plot

1

45

Risk Ratio (M‐H, Random, 95% CI)

2.91 [0.41, 20.48]

Figures and Tables -
Comparison 5. Influenza vaccines versus placebo: randomised controlled trials ‐ live aerosol vaccine ‐ adverse events
Comparison 6. Influenza vaccines versus no vaccination: cohort studies in nursing homes

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

6.1 Influenza Show forest plot

8

1941

Risk Ratio (M‐H, Random, 95% CI)

0.65 [0.32, 1.29]

6.1.1 Outbreak ‐ vaccine matching

4

658

Risk Ratio (M‐H, Random, 95% CI)

1.04 [0.43, 2.51]

6.1.2 Outbreak ‐ vaccine matching absent or unknown

2

592

Risk Ratio (M‐H, Random, 95% CI)

0.47 [0.22, 1.04]

6.1.3 No outbreak ‐ vaccine matching

2

691

Risk Ratio (M‐H, Random, 95% CI)

0.23 [0.05, 1.03]

6.1.4 No outbreak ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

6.2 Influenza‐like illness Show forest plot

26

12388

Risk Ratio (M‐H, Random, 95% CI)

0.76 [0.66, 0.88]

6.2.1 Outbreak ‐ vaccine matching (circulating strains)

16

5963

Risk Ratio (M‐H, Random, 95% CI)

0.77 [0.64, 0.94]

6.2.2 Outbreak ‐ vaccine matching absent or unknown

6

4096

Risk Ratio (M‐H, Random, 95% CI)

0.80 [0.60, 1.05]

6.2.3 No outbreak ‐ vaccine matching

4

2329

Risk Ratio (M‐H, Random, 95% CI)

0.67 [0.46, 0.98]

6.2.4 No outbreak ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

6.3 Pneumonia Show forest plot

17

10274

Risk Ratio (M‐H, Random, 95% CI)

0.53 [0.43, 0.66]

6.3.1 Outbreak ‐ vaccine matching

8

4482

Risk Ratio (M‐H, Random, 95% CI)

0.54 [0.42, 0.70]

6.3.2 Outbreak ‐ vaccine matching absent or unknown

5

3991

Risk Ratio (M‐H, Random, 95% CI)

0.68 [0.39, 1.21]

6.3.3 No outbreak ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

6.3.4 No outbreak ‐ matching absent or unknown

4

1801

Risk Ratio (M‐H, Random, 95% CI)

0.35 [0.18, 0.68]

6.4 Hospitalisation for influenza‐like illness or pneumonia Show forest plot

12

28032

Risk Ratio (M‐H, Random, 95% CI)

0.51 [0.32, 0.81]

6.4.1 Outbreak ‐ vaccine matching

8

2027

Risk Ratio (M‐H, Random, 95% CI)

0.55 [0.36, 0.84]

6.4.2 Outbreak ‐ vaccine matching absent or unknown

2

3301

Risk Ratio (M‐H, Random, 95% CI)

0.82 [0.43, 1.58]

6.4.3 No outbreak ‐ vaccine matching

2

22704

Risk Ratio (M‐H, Random, 95% CI)

0.32 [0.14, 0.76]

6.4.4 No outbreak ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

6.5 Deaths from flu or pneumonia Show forest plot

27

32179

Risk Ratio (M‐H, Random, 95% CI)

0.46 [0.33, 0.63]

6.5.1 Outbreak ‐ vaccine matching

16

6127

Risk Ratio (M‐H, Random, 95% CI)

0.58 [0.41, 0.83]

6.5.2 Outbreak ‐ vaccine matching absent or unknown

4

1089

Risk Ratio (M‐H, Random, 95% CI)

0.34 [0.11, 1.02]

6.5.3 No outbreak ‐ vaccine matching

3

23162

Risk Ratio (M‐H, Random, 95% CI)

0.27 [0.09, 0.87]

6.5.4 No outbreak ‐ vaccine matching absent or unknown

4

1801

Risk Ratio (M‐H, Random, 95% CI)

0.30 [0.14, 0.67]

6.6 All deaths Show forest plot

1

305

Risk Ratio (M‐H, Random, 95% CI)

0.40 [0.21, 0.77]

6.6.1 Outbreak ‐ vaccine matching

1

305

Risk Ratio (M‐H, Random, 95% CI)

0.40 [0.21, 0.77]

6.6.2 Outbreak ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

6.6.3 No outbreak ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

6.6.4 No outbreak ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

6.7 Influenza cases (clinically defined without clear definition) Show forest plot

7

24238

Risk Ratio (M‐H, Random, 95% CI)

0.52 [0.27, 1.02]

6.7.1 Outbreak ‐ vaccine matching

2

271

Risk Ratio (M‐H, Random, 95% CI)

0.70 [0.11, 4.56]

6.7.2 Outbreak ‐ vaccine matching absent or unknown

1

155

Risk Ratio (M‐H, Random, 95% CI)

0.23 [0.09, 0.59]

6.7.3 No outbreak ‐ vaccine matching

1

22462

Risk Ratio (M‐H, Random, 95% CI)

0.40 [0.35, 0.46]

6.7.4 No outbreak ‐ vaccine matching absent or unknown

3

1350

Risk Ratio (M‐H, Random, 95% CI)

0.72 [0.41, 1.28]

Figures and Tables -
Comparison 6. Influenza vaccines versus no vaccination: cohort studies in nursing homes
Comparison 7. Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in nursing homes

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

7.1 Influenza‐like illness Show forest plot

1

1198

Odds Ratio (M‐H, Random, 95% CI)

0.52 [0.40, 0.68]

7.1.1 Outbreak ‐ vaccine matching

1

1198

Odds Ratio (M‐H, Random, 95% CI)

0.52 [0.40, 0.68]

Figures and Tables -
Comparison 7. Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in nursing homes
Comparison 8. Influenza vaccines versus no vaccination: cohort studies in community‐dwellers

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

8.1 Influenza Show forest plot

2

18249

Risk Ratio (M‐H, Random, 95% CI)

0.19 [0.02, 2.01]

8.1.1 Epidemic year ‐ vaccine matching

1

427

Risk Ratio (M‐H, Random, 95% CI)

0.05 [0.01, 0.37]

8.1.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.1.3 Non‐epidemic year ‐ vaccine matching

1

17822

Risk Ratio (M‐H, Random, 95% CI)

0.50 [0.27, 0.91]

8.1.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.2 Influenza‐like illness Show forest plot

4

9613

Risk Ratio (M‐H, Random, 95% CI)

0.75 [0.42, 1.33]

8.2.1 Epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.2.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.2.3 Non‐epidemic year ‐ vaccine matching

2

4636

Risk Ratio (M‐H, Random, 95% CI)

1.08 [0.58, 2.03]

8.2.4 Non‐epidemic year ‐ vaccine matching absent or unknown

1

268

Risk Ratio (M‐H, Random, 95% CI)

0.85 [0.16, 4.55]

8.2.5 Epidemic year ‐ vaccine not matching

1

4709

Risk Ratio (M‐H, Random, 95% CI)

0.44 [0.24, 0.81]

8.3 Pneumonia Show forest plot

2

18090

Risk Ratio (M‐H, Random, 95% CI)

0.88 [0.64, 1.20]

8.3.1 Epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.3.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.3.3 Non‐epidemic year ‐ vaccine matching

1

17822

Risk Ratio (M‐H, Random, 95% CI)

0.87 [0.63, 1.19]

8.3.4 Non‐epidemic year ‐ vaccine matching absent or unknown

1

268

Risk Ratio (M‐H, Random, 95% CI)

3.00 [0.16, 57.42]

8.4 Hospitalisation for flu or pneumonia Show forest plot

9

784643

Risk Ratio (M‐H, Random, 95% CI)

0.73 [0.62, 0.85]

8.4.1 Epidemic year ‐ vaccine matching

6

727776

Risk Ratio (M‐H, Random, 95% CI)

0.74 [0.62, 0.88]

8.4.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.4.3 Non‐epidemic year ‐ vaccine matching

1

25532

Risk Ratio (M‐H, Random, 95% CI)

0.55 [0.37, 0.83]

8.4.4 Non‐epidemic year ‐ vaccine matching absent or unknown

1

26626

Risk Ratio (M‐H, Random, 95% CI)

0.73 [0.54, 0.99]

8.4.5 Epidemic year ‐ vaccine not matching

1

4709

Risk Ratio (M‐H, Random, 95% CI)

0.89 [0.33, 2.40]

8.5 Hospitalisation for any respiratory disease Show forest plot

5

567299

Risk Ratio (M‐H, Random, 95% CI)

0.88 [0.54, 1.43]

8.5.1 Epidemic year ‐ vaccine matching

3

515141

Risk Ratio (M‐H, Random, 95% CI)

0.78 [0.37, 1.64]

8.5.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.5.3 Non‐epidemic year ‐ vaccine matching

1

25532

Risk Ratio (M‐H, Random, 95% CI)

0.94 [0.79, 1.12]

8.5.4 Non‐epidemic year ‐ vaccine matching absent or unknown

1

26626

Risk Ratio (M‐H, Random, 95% CI)

1.16 [1.01, 1.34]

8.6 Deaths from flu or pneumonia Show forest plot

1

163391

Risk Ratio (M‐H, Random, 95% CI)

0.87 [0.70, 1.09]

8.6.1 Epidemic year ‐ vaccine matching

1

163391

Risk Ratio (M‐H, Random, 95% CI)

0.87 [0.70, 1.09]

8.6.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.6.3 Non‐epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.6.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.7 Deaths from respiratory disease Show forest plot

1

426668

Risk Ratio (M‐H, Random, 95% CI)

1.32 [1.25, 1.39]

8.7.1 Epidemic year ‐ vaccine matching

1

426668

Risk Ratio (M‐H, Random, 95% CI)

1.32 [1.25, 1.39]

8.8 All deaths Show forest plot

8

409468

Risk Ratio (M‐H, Random, 95% CI)

0.61 [0.47, 0.80]

8.8.1 Epidemic year ‐ vaccine matching

4

300332

Risk Ratio (M‐H, Random, 95% CI)

0.59 [0.50, 0.70]

8.8.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.8.3 Non‐epidemic year ‐ vaccine matching

3

104427

Risk Ratio (M‐H, Random, 95% CI)

0.65 [0.30, 1.39]

8.8.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.8.5 Epidemic year ‐ vaccine not matching

1

4709

Risk Ratio (M‐H, Random, 95% CI)

3.89 [0.90, 16.89]

8.9 Hospitalisation for heart disease Show forest plot

6

433934

Risk Ratio (M‐H, Random, 95% CI)

0.87 [0.67, 1.12]

8.9.1 Epidemic year ‐ vaccine matching

4

381776

Risk Ratio (M‐H, Random, 95% CI)

0.74 [0.56, 0.97]

8.9.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

8.9.3 Non‐epidemic year ‐ vaccine matching

1

25532

Risk Ratio (M‐H, Random, 95% CI)

1.06 [0.81, 1.38]

8.9.4 Non‐epidemic year ‐ vaccine matching absent or unknown

1

26626

Risk Ratio (M‐H, Random, 95% CI)

1.59 [1.07, 2.36]

8.10 Combined outcome: all deaths or severe respiratory illness Show forest plot

3

290819

Risk Ratio (M‐H, Random, 95% CI)

0.71 [0.58, 0.85]

8.10.1 Epidemic year ‐ vaccine matching

2

132365

Risk Ratio (M‐H, Random, 95% CI)

0.80 [0.42, 1.55]

8.10.2 Epidemic year ‐ vaccine matching absent or unknown

1

158454

Risk Ratio (M‐H, Random, 95% CI)

0.74 [0.69, 0.80]

Figures and Tables -
Comparison 8. Influenza vaccines versus no vaccination: cohort studies in community‐dwellers
Comparison 9. Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

9.1 Hospitalisation for influenza or pneumonia Show forest plot

8

Odds Ratio (IV, Random, 95% CI)

0.73 [0.67, 0.79]

9.1.1 Epidemic ‐ vaccine matching

6

Odds Ratio (IV, Random, 95% CI)

0.71 [0.65, 0.77]

9.1.2 Non‐epidemic ‐ vaccine not matching

1

Odds Ratio (IV, Random, 95% CI)

0.90 [0.58, 1.38]

9.1.3 Epidemic year ‐ vaccine matching absent or unknown

1

Odds Ratio (IV, Random, 95% CI)

0.82 [0.68, 0.98]

9.2 Hospitalisation for any respiratory disease Show forest plot

13

Odds Ratio (IV, Random, 95% CI)

0.78 [0.72, 0.85]

9.2.1 Epidemic ‐ vaccine matching

9

Odds Ratio (IV, Random, 95% CI)

0.71 [0.67, 0.74]

9.2.2 Non‐epidemic ‐ vaccine not matching

2

Odds Ratio (IV, Random, 95% CI)

0.91 [0.76, 1.08]

9.2.3 Non‐epidemic year ‐ vaccine matching

2

Odds Ratio (IV, Random, 95% CI)

0.94 [0.84, 1.06]

9.3 Hospitalisation for heart disease Show forest plot

6

Odds Ratio (IV, Random, 95% CI)

0.76 [0.70, 0.82]

9.3.1 Epidemic year ‐ vaccine matching

5

Odds Ratio (IV, Random, 95% CI)

0.75 [0.70, 0.82]

9.3.2 Non‐epidemic ‐ vaccine not matching

1

Odds Ratio (IV, Random, 95% CI)

0.80 [0.55, 1.16]

9.4 All deaths Show forest plot

7

Odds Ratio (IV, Random, 95% CI)

0.53 [0.46, 0.61]

9.4.1 Epidemic year ‐ vaccine matching

5

Odds Ratio (IV, Random, 95% CI)

0.47 [0.42, 0.53]

9.4.2 Epidemic year ‐ vaccine matching absent or unknown

1

Odds Ratio (IV, Random, 95% CI)

0.65 [0.57, 0.75]

9.4.3 Non‐epidemic year ‐ vaccine matching

1

Odds Ratio (IV, Random, 95% CI)

0.76 [0.60, 0.97]

9.5 Combined outcome: all deaths or severe respiratory illness Show forest plot

1

Odds Ratio (IV, Random, 95% CI)

0.70 [0.37, 1.34]

9.5.1 Epidemic year ‐ vaccine matching

1

Odds Ratio (IV, Random, 95% CI)

0.70 [0.37, 1.34]

Figures and Tables -
Comparison 9. Influenza vaccines versus no vaccination: cohort studies in community ‐ adjusted rates
Comparison 10. Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

10.1 Influenza Show forest plot

1

6423

Risk Ratio (M‐H, Random, 95% CI)

0.40 [0.14, 1.17]

10.1.1 Epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.1.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.1.3 Non‐epidemic year ‐ vaccine matching

1

6423

Risk Ratio (M‐H, Random, 95% CI)

0.40 [0.14, 1.17]

10.1.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.2 Pneumonia Show forest plot

1

6423

Risk Ratio (M‐H, Random, 95% CI)

1.22 [0.76, 1.94]

10.2.1 Epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.2.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.2.3 Non‐epidemic year ‐ vaccine matching

1

6423

Risk Ratio (M‐H, Random, 95% CI)

1.22 [0.76, 1.94]

10.2.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.3 Hospitalisation for influenza or pneumonia Show forest plot

1

45932

Risk Ratio (M‐H, Random, 95% CI)

0.74 [0.63, 0.86]

10.3.1 Epidemic year ‐ vaccine matching

1

45932

Risk Ratio (M‐H, Random, 95% CI)

0.74 [0.63, 0.86]

10.3.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.3.3 Non‐epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.3.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.4 Hospitalisation for any respiratory disease Show forest plot

2

189004

Risk Ratio (M‐H, Random, 95% CI)

0.85 [0.80, 0.92]

10.4.1 Epidemic year ‐ vaccine matching

2

189004

Risk Ratio (M‐H, Random, 95% CI)

0.85 [0.80, 0.92]

10.4.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.4.3 Non‐epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.4.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.5 Deaths from respiratory disease Show forest plot

1

142464

Risk Ratio (M‐H, Random, 95% CI)

0.92 [0.86, 0.98]

10.5.1 Epidemic year ‐ vaccine matching

1

142464

Risk Ratio (M‐H, Random, 95% CI)

0.92 [0.86, 0.98]

10.6 All deaths Show forest plot

3

68032

Risk Ratio (M‐H, Random, 95% CI)

0.39 [0.16, 0.97]

10.6.1 Epidemic year ‐ vaccine matching

1

2344

Risk Ratio (M‐H, Random, 95% CI)

0.13 [0.02, 0.92]

10.6.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.6.3 Non‐epidemic year ‐ vaccine matching

2

65688

Risk Ratio (M‐H, Random, 95% CI)

0.47 [0.17, 1.28]

10.6.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.7 Hospitalisation for heart disease Show forest plot

1

45932

Risk Ratio (M‐H, Random, 95% CI)

0.92 [0.83, 1.03]

10.7.1 Epidemic year ‐ vaccine matching

1

45932

Risk Ratio (M‐H, Random, 95% CI)

0.92 [0.83, 1.03]

10.7.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.7.3 Non‐epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.7.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

10.8 Combined outcome: all deaths or severe respiratory illness Show forest plot

2

146248

Risk Ratio (M‐H, Random, 95% CI)

0.60 [0.49, 0.74]

10.8.1 Epidemic year ‐ vaccine matching

1

54438

Risk Ratio (M‐H, Random, 95% CI)

0.54 [0.49, 0.60]

10.8.2 Epidemic year ‐ vaccine matching absent or unknown

1

91810

Risk Ratio (M‐H, Random, 95% CI)

0.67 [0.61, 0.72]

Figures and Tables -
Comparison 10. Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ risk groups
Comparison 11. Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

11.1 Influenza Show forest plot

1

11399

Risk Ratio (M‐H, Random, 95% CI)

0.57 [0.27, 1.17]

11.1.1 Epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.1.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.1.3 Non‐epidemic year ‐ vaccine matching

1

11399

Risk Ratio (M‐H, Random, 95% CI)

0.57 [0.27, 1.17]

11.1.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.2 Pneumonia Show forest plot

1

11399

Risk Ratio (M‐H, Random, 95% CI)

0.59 [0.37, 0.92]

11.2.1 Epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.2.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.2.3 Non‐epidemic year ‐ vaccine matching

1

11399

Risk Ratio (M‐H, Random, 95% CI)

0.59 [0.37, 0.92]

11.2.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.3 Hospitalisation for influenza or pneumonia Show forest plot

1

101619

Risk Ratio (M‐H, Random, 95% CI)

0.50 [0.40, 0.63]

11.3.1 Epidemic year ‐ vaccine matching

1

101619

Risk Ratio (M‐H, Random, 95% CI)

0.50 [0.40, 0.63]

11.3.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.3.3 Non‐epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.3.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.4 Hospitalisation for any respiratory disease Show forest plot

2

376324

Risk Ratio (M‐H, Random, 95% CI)

0.84 [0.55, 1.27]

11.4.1 Epidemic year ‐ vaccine matching

2

376324

Risk Ratio (M‐H, Random, 95% CI)

0.84 [0.55, 1.27]

11.4.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.4.3 Non‐epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.4.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.5 Deaths from respiratory disease Show forest plot

1

281424

Risk Ratio (M‐H, Random, 95% CI)

1.41 [1.31, 1.53]

11.5.1 Epidemic year ‐ vaccine matching

1

281424

Risk Ratio (M‐H, Random, 95% CI)

1.41 [1.31, 1.53]

11.6 All deaths Show forest plot

3

43821

Risk Ratio (M‐H, Random, 95% CI)

0.65 [0.33, 1.29]

11.6.1 Epidemic year ‐ vaccine matching

1

7047

Risk Ratio (M‐H, Random, 95% CI)

1.09 [0.26, 4.49]

11.6.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.6.3 Non‐epidemic year ‐ vaccine matching

2

36774

Risk Ratio (M‐H, Random, 95% CI)

0.59 [0.27, 1.30]

11.6.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.7 Hospitalisation for heart disease Show forest plot

1

101619

Risk Ratio (M‐H, Random, 95% CI)

0.79 [0.61, 1.01]

11.7.1 Epidemic year ‐ vaccine matching

1

101619

Risk Ratio (M‐H, Random, 95% CI)

0.79 [0.61, 1.01]

11.7.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.7.3 Non‐epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.7.4 Non‐epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

11.8 Combined outcome: all deaths or severe respiratory illness Show forest plot

2

135180

Risk Ratio (M‐H, Random, 95% CI)

0.62 [0.54, 0.70]

11.8.1 Epidemic year ‐ vaccine matching

1

68536

Risk Ratio (M‐H, Random, 95% CI)

0.65 [0.54, 0.78]

11.8.2 Epidemic year ‐ vaccine matching absent or unknown

1

66644

Risk Ratio (M‐H, Random, 95% CI)

0.58 [0.48, 0.71]

Figures and Tables -
Comparison 11. Influenza vaccines versus no vaccination: cohort studies in community‐dwellers ‐ no risk groups
Comparison 12. Influenza and pneumococcal vaccines versus no vaccination: cohort studies in community‐dwellers

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

12.1 Influenza‐like illness Show forest plot

1

374

Risk Ratio (M‐H, Random, 95% CI)

0.32 [0.16, 0.64]

12.1.1 Epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

12.1.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

12.1.3 Non‐epidemic year ‐ vaccine matching

1

374

Risk Ratio (M‐H, Random, 95% CI)

0.32 [0.16, 0.64]

12.2 Hospitalisation for influenza or pneumonia or respiratory disease Show forest plot

3

518748

Risk Ratio (M‐H, Random, 95% CI)

0.67 [0.64, 0.70]

12.2.1 Epidemic year ‐ vaccine matching

2

518374

Risk Ratio (M‐H, Random, 95% CI)

0.67 [0.63, 0.71]

12.2.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

12.2.3 Non‐epidemic year ‐ vaccine matching

1

374

Risk Ratio (M‐H, Random, 95% CI)

0.90 [0.10, 7.97]

12.3 Deaths from influenza or pneumonia Show forest plot

1

259627

Risk Ratio (M‐H, Random, 95% CI)

0.43 [0.33, 0.57]

12.3.1 Epidemic year ‐ vaccine matching

1

259627

Risk Ratio (M‐H, Random, 95% CI)

0.43 [0.33, 0.57]

12.3.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

12.3.3 Non‐epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

12.4 All deaths Show forest plot

2

260001

Risk Ratio (M‐H, Random, 95% CI)

0.44 [0.41, 0.46]

12.4.1 Epidemic year ‐ vaccine matching

1

259627

Risk Ratio (M‐H, Random, 95% CI)

0.44 [0.41, 0.46]

12.4.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

12.4.3 Non‐epidemic year ‐ vaccine matching

1

374

Risk Ratio (M‐H, Random, 95% CI)

1.60 [0.08, 30.65]

Figures and Tables -
Comparison 12. Influenza and pneumococcal vaccines versus no vaccination: cohort studies in community‐dwellers
Comparison 13. Influenza vaccines with adjuvant versus no vaccination: cohort studies in community‐dwellers

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

13.1 Influenza‐like illness Show forest plot

2

498

Risk Ratio (M‐H, Random, 95% CI)

0.30 [0.16, 0.56]

13.1.1 Epidemic year ‐ vaccine matching

1

263

Risk Ratio (M‐H, Random, 95% CI)

0.20 [0.07, 0.54]

13.1.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

13.1.3 Non‐epidemic year ‐ vaccine matching

1

235

Risk Ratio (M‐H, Random, 95% CI)

0.38 [0.18, 0.82]

13.2 Hospitalisation for influenza or pneumonia or respiratory disease Show forest plot

2

498

Risk Ratio (M‐H, Random, 95% CI)

0.17 [0.02, 1.28]

13.2.1 Epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

13.2.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

13.2.3 Non‐epidemic year ‐ vaccine matching

2

498

Risk Ratio (M‐H, Random, 95% CI)

0.17 [0.02, 1.28]

13.3 All deaths Show forest plot

1

235

Risk Ratio (M‐H, Random, 95% CI)

2.10 [0.10, 43.10]

13.3.1 Epidemic year ‐ vaccine matching

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

13.3.2 Epidemic year ‐ vaccine matching absent or unknown

0

0

Risk Ratio (M‐H, Random, 95% CI)

Not estimable

13.3.3 Non‐epidemic year ‐ vaccine matching

1

235

Risk Ratio (M‐H, Random, 95% CI)

2.10 [0.10, 43.10]

Figures and Tables -
Comparison 13. Influenza vaccines with adjuvant versus no vaccination: cohort studies in community‐dwellers
Comparison 14. Influenza vaccines versus no vaccination: case‐control studies in community

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

14.1 Hospitalisations for influenza or pneumonia Show forest plot

2

1074

Odds Ratio (M‐H, Random, 95% CI)

0.89 [0.69, 1.15]

14.1.1 Outbreak ‐ vaccine matching (circulating strains)

0

0

Odds Ratio (M‐H, Random, 95% CI)

Not estimable

14.1.2 Outbreak ‐ vaccine matching absent or unknown

1

825

Odds Ratio (M‐H, Random, 95% CI)

0.92 [0.69, 1.22]

14.1.3 No outbreak ‐ vaccine matching

1

249

Odds Ratio (M‐H, Random, 95% CI)

0.82 [0.48, 1.40]

14.2 Hospitalisations for any respiratory disease Show forest plot

4

21378

Odds Ratio (M‐H, Random, 95% CI)

1.08 [0.95, 1.23]

14.2.1 Outbreak ‐ vaccine matching

3

20582

Odds Ratio (M‐H, Random, 95% CI)

1.08 [0.92, 1.26]

14.2.2 No outbreak ‐ not matching

1

796

Odds Ratio (M‐H, Random, 95% CI)

1.02 [0.68, 1.52]

14.3 Deaths from influenza or pneumonia Show forest plot

1

1092

Odds Ratio (M‐H, Random, 95% CI)

0.74 [0.53, 1.04]

14.3.1 Outbreak ‐ vaccine matching

1

1092

Odds Ratio (M‐H, Random, 95% CI)

0.74 [0.53, 1.04]

14.4 Pneumonia (no better defined) Show forest plot

1

519

Odds Ratio (M‐H, Fixed, 95% CI)

0.87 [0.57, 1.33]

14.4.1 Outbreak ‐ partially matching

1

519

Odds Ratio (M‐H, Fixed, 95% CI)

0.87 [0.57, 1.33]

Figures and Tables -
Comparison 14. Influenza vaccines versus no vaccination: case‐control studies in community
Comparison 15. Influenza vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

15.1 Hospitalisations for influenza or pneumonia Show forest plot

5

Odds Ratio (IV, Random, 95% CI)

0.59 [0.47, 0.74]

15.1.1 Epidemic ‐ vaccine matching

1

Odds Ratio (IV, Random, 95% CI)

0.55 [0.36, 0.85]

15.1.2 Non‐epidemic ‐ vaccine not matching

0

Odds Ratio (IV, Random, 95% CI)

Not estimable

15.1.3 Epidemic year ‐ vaccine matching absent or unknown

2

Odds Ratio (IV, Random, 95% CI)

0.68 [0.58, 0.79]

15.1.4 Non‐epidemic ‐ vaccine matching

2

Odds Ratio (IV, Random, 95% CI)

0.37 [0.16, 0.87]

15.2 Hospitalisations for any respiratory disease Show forest plot

3

Odds Ratio (IV, Random, 95% CI)

0.71 [0.56, 0.90]

15.2.1 Epidemic ‐ vaccine matching

3

Odds Ratio (IV, Random, 95% CI)

0.71 [0.56, 0.90]

15.2.2 Non‐epidemic ‐ vaccine matching

0

Odds Ratio (IV, Random, 95% CI)

Not estimable

15.2.3 Non‐epidemic year ‐ vaccine matching

0

Odds Ratio (IV, Random, 95% CI)

Not estimable

15.3 Deaths from pneumonia or influenza Show forest plot

2

Odds Ratio (IV, Random, 95% CI)

0.74 [0.60, 0.92]

15.3.1 Epidemic year ‐ vaccine matching

1

Odds Ratio (IV, Random, 95% CI)

0.76 [0.60, 0.97]

15.3.2 Epidemic year ‐ vaccine matching absent or unknown

1

Odds Ratio (IV, Random, 95% CI)

0.67 [0.42, 1.07]

Figures and Tables -
Comparison 15. Influenza vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates
Comparison 16. Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in community

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

16.1 Hospitalisations for influenza or pneumonia Show forest plot

4

6629

Odds Ratio (M‐H, Random, 95% CI)

0.97 [0.85, 1.09]

16.1.1 Outbreak ‐ vaccine matching

2

3617

Odds Ratio (M‐H, Random, 95% CI)

0.95 [0.69, 1.31]

16.1.2 No outbreak ‐ vaccine matching

2

3012

Odds Ratio (M‐H, Random, 95% CI)

0.93 [0.80, 1.08]

Figures and Tables -
Comparison 16. Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in community
Comparison 17. Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

17.1 Hospitalisations for influenza or pneumonia Show forest plot

2

Odds Ratio (IV, Random, 95% CI)

0.68 [0.54, 0.86]

17.1.1 Epidemic ‐ vaccine matching

1

Odds Ratio (IV, Random, 95% CI)

0.68 [0.50, 0.93]

17.1.2 Non‐epidemic ‐ vaccine not matching

0

Odds Ratio (IV, Random, 95% CI)

Not estimable

17.1.3 Epidemic year ‐ vaccine matching absent or unknown

0

Odds Ratio (IV, Random, 95% CI)

Not estimable

17.1.4 Non‐epidemic ‐ vaccine matching

1

Odds Ratio (IV, Random, 95% CI)

0.69 [0.49, 0.97]

Figures and Tables -
Comparison 17. Influenza and pneumococcal vaccines versus no vaccination: case‐control studies in community ‐ adjusted rates
Comparison 18. Sensitivity analysis: comparison 01: subgroup analysis by study quality

Outcome or subgroup title

No. of studies

No. of participants

Statistical method

Effect size

18.1 Influenza‐like illness Show forest plot

25

9211

Risk Ratio (M‐H, Random, 95% CI)

0.75 [0.65, 0.87]

18.1.1 Quality A

8

4502

Risk Ratio (M‐H, Random, 95% CI)

0.78 [0.65, 0.94]

18.1.2 Quality B

13

3854

Risk Ratio (M‐H, Random, 95% CI)

0.82 [0.65, 1.03]

18.1.3 Quality C

3

389

Risk Ratio (M‐H, Random, 95% CI)

0.66 [0.43, 1.00]

18.1.4 Quality D

1

466

Risk Ratio (M‐H, Random, 95% CI)

0.44 [0.35, 0.57]

Figures and Tables -
Comparison 18. Sensitivity analysis: comparison 01: subgroup analysis by study quality