Does influenza vaccination prevent asthma exacerbations in children?

Objective: Influenza can exacerbate asthma, particularly in children. The e ffectiveness of influenza vaccine in preventing influenza-related asthma ex acerbations, however, is not known. We evaluated influenza vaccine effectiv eness in protecting children against influenza-related asthma exacerbations . Study design: We conducted a population-based retrospective cohort study wi th medical and vaccination records in 4 large health maintenance organizati ons in the United States during the 1993-1994, 1994-1995, and 1995-1996 inf luenza seasons. We studied children with asthma who were 1 through 6 years of age and who were identified by search of computerized databases of medic al encounters and pharmacy dispensings. Main outcome measures were exacerba tions of asthma evaluated in the emergency department or hospital. Results: Unadjusted rates of asthma exacerbations were higher after influen za vaccination than before vaccination. After adjustment was done for asthm a severity by means of a self-control method, however, the incidence rate r atios of asthma exacerbations after vaccination were 0.78 (95% CI: 0.55 to 1.10), 0.59 (0.43 to 0.81), and 0.65 (0.52 to 0.80) compared with the perio d before vaccination during the 3 influenza seasons. Conclusions: After controlling for asthma severity, we found that influenza vaccination protects against acute asthma exacerbations in children.