The effect of influenza vaccination on risk of acute myocardial infarction: Self-controlled case-series study

Acute myocardial infarction (AMI) peaks in winter months, partly linked to epidemic influenza. This implies that influenza vaccination may prevent some cases of AMI. This study investigated the association between influenza vaccination and AMI using the self-controlled case-series method. We identified 8180 cases of first AMI aged 40 years and over at time of diagnosis. The incidence of AMI was significantly reduced in the 60 days following vaccination (compared with the baseline period), ranging from a reduction of 32% (IRR 0.68; 95% CI 0.60-0.78) at 1-14 days after vaccination, to 18% (IRR 0.82; 95% CI 0.75-0.90) at 29-59 days after vaccination. Reductions in AMI incidence were more pronounced for early seasonal vaccinations before mid-November.