Study on the Effect of Influenza Vaccination After Heart Attack on Future Cardiovascular Prognosis

Background. For more than a century a causal link between influenza and cardiovascular disease has been suspected. It is conceivable that influenza may precipitate plaque rupture, increase cytokines with central roles in plaque destabilization and trigger the coagulation cascade. Accordingly, registry studies, case control studies and a few small randomized trials, all underpowered for clinical endpoints, have demonstrated that the risk for acute myocardial infarction (AMI) is increased following respiratory infection and that the risk of stroke and AMI in patients with established cardiovascular disease seem to be reduced following influenza vaccination. In May 2015 a Cochrane review concluded that influenza vaccination may reduce cardiovascular mortality and cardiovascular events but bias and inconsistent results in prior studies require higher-quality evidence to confirm these findings. High costs and little commercial interest in conducting a randomized trial on influenza vaccine in cardiovascular disease stand in the way. Objective. The objective is to document whether influenza vaccination protects against cardiovascular events and death in patients with an AMI or very high risk stable coronary artery disease patients. Methods. Population: 4400 patients with ST-elevation (STEMI), non-ST elevation myocardial infarction (NSTEMI) or very high risk stable coronary artery disease are randomized 1:1 in a blinded fashion using an RRCT design and followed up via registries and telephone calls. Intervention: Influenza vaccination. Control: Placebo (saline). Outcome: The primary endpoint is a composite of death, myocardial infarction and stent thrombosis till 1 year. Patients will be included in the study in all of Sweden's 7 university hospitals and 5 general hospitals, 4 university hospitals and 1 general hospital in Denmark, in 1 specialized heart center in Norway, 2 university hospitals in Czech Republic, 6 hospitals in Scotland, 1 university hospital in Latvia an