Exacerbations in children with asthma are often associated with viral infections(1). Although the contribution by influenza virus to this exacerbation has not been fully quantified several guidelines recommend immunization of asthmatic subjects against influenza. A question is asked in various forums whether there should be a policy to vaccinate children with influenza vaccine in India. The primary goal of influenza vaccination policy has been the reduction of excess deaths associated with influenza epidemics(2). While influenza may cause asthma exacerbations, there has been concern that vacciantion may precipitate an asthma attack in some people.

One previously done review had concluded that this vaccine does not benefit patients of asthma an chronic obstructive pulmonary disease(3). A recent Cochrane review has addressed this problem systematically to assess the effects of influenza vaccination in children and adults with asthma(4). The source of the articles included in the review was the Cochrane Airways Groups trials register which is a data base maintained by the Cochrane airways group with its editorial base at London. The reference lists of articles were also checked.

Randomized trials of influenza vaccination in children (over two years of age) and adults with asthma were included. People with chronic obstructive pulmonary disease were excluded. 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.

Nine trials were analyzed. Four of these trials were of high quality. The studies covered a wide diversity of people, settings and types of influenza vaccination, so data from the different trials were not pooled. In one trial, no protective effect of influenza vaccination against asthma exacerbation was demonstrated, but the inci-dence of influenza was low during the study period. A higher number of asthma exacerba-tions following killed influenza vaccination was found in one trial (risk difference 3.1%, 95% confidence interval 0.3% to 5.9%). When people with upper respiratory tract infections were excluded, this difference was no longer significant. A small trial using recombinant vaccine found no significant difference in asthma exacerbations between the vaccinated and placebo groups.

The reviewers did not find enough evidence to assess the benefits and risks of influenza vaccination for people with asthma. Whatever evidence is available is not of sufficient quality to assess the usefulness of this vaccine in asthmatic subjects. It has been recommended that large randomized controlled trials be conducted with sufficient power to detect the difference in the exacerbation rate amongst these individuals. Moreover, in countries like India where enough information is not available about the prevailing influenza virus strains this vaccine which has a potential to be ineffective after a few years even in the countries where it is produced cannot be routinely recommended.

1. McIntosh K, Ellis EF, Hoffman LS, Lyban TG, Ellis JJ, Fulginiti VA. The association of viral and bacterial respiratory infections with exacerbation of wheezing in young asthmatics. J Pediatr 1973; 82: 578-590.

2. Barker WH, Mulloly JP. Pneumonia and influenza deaths during epidemics. Arch Int med 1982; 142: 85-89.

3. Rothbath PH, Kemper BM, Sprenger MJ. Sense and nonsense of influenza vaccination in asthma and chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1995; 151: 1682-1686.

4. Cates CJ, Jefferson TO, Bara AL. Vaccines for preventing influenza in people with asthma. The Cochrane Library, 1999, Issue 4. Update Software. Oxford, UK.