The safety of inactivated influenza vaccine in adults and children with asthma

Background: Influenza causes substantial morbidity in adults and children w ith asthma, and vaccination can prevent influenza and its complications. Ho wever, there is concern that vaccination may cause exacerbations of asthma. Methods: To investigate the safety of the inactivated trivalent split-virus influenza vaccine in adults and children with asthma, we conducted a multi center, randomized, double-blind, placebo-controlled, crossover trial in 20 32 patients with asthma (age range, 3 to 64 years). The order of injection of vaccine and placebo was assigned randomly, with a mean of 22 days betwee n the injections. Each day during the two weeks after each injection, the p atients recorded peak expiratory flow rates, symptoms thought to be related to the injection, use of asthma medications, unscheduled health care visit s for asthma, and asthma-related absences from school or work. The primary outcome measure was an exacerbation of asthma in the two weeks after the in jections. Results: The frequency of exacerbations of asthma was similar in the two we eks after the influenza vaccination and after placebo injection (28.8 perce nt and 27.7 percent, respectively; absolute difference, 1.1 percent; 95 per cent confidence interval, -1.4 percent to 3.6 percent). The exacerbation ra tes were similar in subgroups defined according to age, severity of asthma, and other factors. Among symptoms thought to be associated with the inject ion, only body aches were more frequent after the vaccine injection than af ter placebo injection (25.1 percent vs. 20.8 percent, P<0.001). Conclusions: The inactivated influenza vaccine is safe to administer to adu lts and children with asthma, including those with severe asthma. Given the morbidity of influenza, all those with asthma should receive the vaccine a nnually. (N Engl J Med 2001;345:1529-36.) Copyright (C) 2001 Massachusetts Medical Society.