Vaccines for preventing influenza in people with asthma
Abstract
Background
Influenza vaccination is recommended for asthmatic patients in many countries as observational studies have shown that influenza infection can be associated with asthma exacerbations, but influenza vaccination itself has the potential to adversely affect pulmonary function. A recent overview concluded that there was no clear benefit of influenza vaccination in patients with asthma but this conclusion was not based on a systematic search of the literature.
Objectives
Whilst influenza may cause asthma exacerbations, there is controversy about the use of influenza vaccinations, since they may precipitate an asthma attack in some people. The objective of this review was to assess the efficacy of influenza vaccination in children and adults with asthma.
Search methods
We searched the Cochrane Airways Group trials register and checked reference lists of articles. The last search was carried out in February 2004.
Selection criteria
Randomised trials of influenza vaccination in children (over two years of age) and adults with asthma. Studies involving people with chronic obstructive pulmonary disease were excluded.
Data collection and analysis
Inclusion criteria and assessment of trial quality were applied by two reviewers independently. Data extraction was done by two reviewers independently. Study authors were contacted for missing information.
Main results
Nine trials were initially included. Four of these trials were of high quality. Five further articles have been included in two updates (Bueving 2002; Castro 2001; Redding 2002; Reid 1998). The included studies covered a wide diversity of people, settings and types of influenza vaccination, but data from the more recent studies that used similar vaccines have been pooled. The pooled results of two trials involving 2306 people with asthma did not demonstrate a significant increase in asthma exacerbations in the two weeks following influenza vaccination (Risk Difference 0.00; 95% confidence interval ‐0.02 to 0.02). A recent study on 696 children with asthma did not demonstrate a significant reduction in influenza related asthma exacerbations (Risk Difference 0.01; 95% confidence interval ‐0.02 to 0.04). An udpate search in February 2004 did not identify any new studies.
Authors' conclusions
Evidence from recently published trials indicates that there is no significant increase in asthma exacerbations immediately after vaccination (at least with inactivated influenza vaccination); however, uncertainty remains about the degree of protection vaccination affords against asthma exacerbations that are related to influenza infection.
PICOs
Plain language summary
Influenza vaccine now seems unlikely to worsen asthma, but research is needed to determine whether asthma attacks are prevented by influenza vaccination
Influenza (flu) is a highly infectious disease, caused by viruses. Influenza has been thought to cause asthma attacks. Newly published research suggests that the vaccine against influenza is unlikely to precipitate asthma attacks for a few days after the vaccine is used. Few trials have been carried out in a way that tests whether asthma attacks following influenza infection (as opposed to following the vaccination) are significantly reduced by having influenza vaccination, so uncertainty remains in terms of how much difference vaccination makes to people with asthma.
