Influenza vaccination and risk of incident myocardial infarction

Background: Several studies suggest that influenza vaccination may be associated with a decreased risk of acute cardiovascular events. We examined the association between influenza vaccination and risk of incident myocardial infarction (MI) in persons at least 65 years of age in a population-based case-control study. Methods: Case subjects were members of Group Health Cooperative (GHC), a health maintenance organization, with incident MI during 1992-1998. Control subjects were GHC members without a history of MI who were frequency matched to case subjects by age, sex, calendar year, and presence of treated hypertension. The medical records of 750 case subjects with MI and 1735 controls were reviewed. Results: Receipt of influenza vaccine was not associated with risk of incident MI during the months of November through March (odds ratio [OR]: 0.97, 95% confidence interval [Cl]: 0.75-1.27) or April through September (OR: 0.97, 95% Cl 0.75-1.26). Conclusions: This study does not provide evidence supporting an association of influenza vaccination and reduction in risk of myocardial infarction.