© 2005 American Thoracic Society
Influenza Vaccination in Children with AsthmaNo Reason to Change Current RecommendationsTo the Editor:Dr. Bueving and colleagues described a study in The Netherlands on the effect of influenza vaccination of children with asthma on the incidence of exacerbations of the disease (1). The authors concluded that "influenza vaccination did not result in significant reduction of the number ... of asthma exacerbations caused by influenza." Although this statement does reflect their findings, it can easily be misinterpreted when considering vaccination policy, particularly since influenza incidence in the period under study was too low to draw definitive conclusions. The study was not designed to first evaluate the efficacy of influenza vaccine to prevent infection and uncomplicated disease, and then to determine whether exacerbations were present. Instead, it was set up only to identify exacerbations when they reached a defined level of severity, and then to collect specimens at that point, often late in the illness. This requires relatively large numbers, since only a fraction of infections will produce an exacerbation. The authors combined the 2 years in spite of the differing circulating viruses, types A (H3N2) in Year 1 and (H1N1) in Year 2. There were opposing findings in the two winters slightly favoring vaccination in Year 1 and placebo in Year 2. Recruitment to the study included children and adolescents with asthma aged 6–18 years. We would be interested to know if (and how many) of the children with asthma registered in participating practices were routinely vaccinated and, if in consequence, the children with more severe asthma were excluded from the study. Most importantly, power calculations were based on projected incidence rates of influenza that were too high, a difficulty compounded by more than half the subjects being recruited in a particularly mild influenza season (2). Other studies have shown that influenza vaccine prevents influenza in children, and that influenza produces asthma exacerbations in children (3, 4). Vaccine safety has been clearly documented (5). We would strongly endorse the authors' plea for further research in this area, but do not think it prudent at this time to alter influenza policy. We would also suggest that studies of this nature should include virology for respiratory syncytial virus, which typically co-circulates, particularly in younger children (6). Many respiratory viruses have been repeatedly documented to produce exacerbations of asthma in children, but influenza is the only one for which a vaccine of proven efficacy is available.
a Royal College of General Practitioners Birmingham, United Kingdom FOOTNOTES Conflict of Interest Statement: D.M.F. has received consultancy fees from pharmaceutical manufacturers and has been supported to attend meetings all in relation to influenza vaccinations, treatment, and surveillance, but these have not exceeded $10,000 in the last three years; A.S.M. participated on the U.S. Advisory Board of Solvay Pharmaceuticals, Inc. REFERENCES
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