Ecological, case-control, cohort, case-only and randomised controlled trials (RCTs) that evaluated the effects of influenza vaccination on the outcomes myocardial infarction or death from cardiovascular disease (or more specific causes) were eligible for inclusion. Studies with insufficient description of study methods were excluded.
The review of effectiveness of influenza vaccines on cardiac outcomes included RCTs of patients with acute myocardial infarction, patients that received elective percutaneous coronary intervention (with a history of acute myocardial infarction, unstable angina, coronary artery bypass graft or percutaneous coronary intervention) and patients with angiographically-confirmed coronary artery disease. Studies compared influenza vaccine with control,
The authors stated neither how studies were selected for the review nor how many reviewers performed the selection.