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Influenza vaccines for preventing coronary heart disease.

BACKGROUND
Vaccination against influenza may reduce the risk of coronary heart disease. However the evidence is scarce and the size of the benefit is unknown.


OBJECTIVES
To assess the potential benefit of influenza vaccination for primary and secondary prevention of coronary heart disease.


SEARCH STRATEGY
We searched the Cochrane Central Register of Controlled Trials, Issue 4 2007, MEDLINE (2005 to January 2008) and EMBASE (2005 to January 2008). Furthermore, we searched databases for recent or ongoing trials and reference lists of articles. Lastly, we contacted pharmaceutical companies for non published data or trials on influenza vaccination. No language restrictions were applied.


SELECTION CRITERIA
Randomised clinical trials of influenza vaccination compared to placebo or no treatment in primary or secondary prevention with outcome on coronary heart disease.


DATA COLLECTION AND ANALYSIS
Data extraction and the assessment of quality was done with a predefined form by two review authors independently. We contacted investigators when data on the outcome were missing.


MAIN RESULTS
In the two included trials, 778 participants were randomised to vaccination or placebo. Only 39 participants died a cardiovascular death. In addition, only 35 participants had an acute myocardial infarction. Consequently, estimates of treatment effects were imprecise.


AUTHORS' CONCLUSIONS
Despite the significant effect noted in the studies, we concluded that there are not enough data to evaluate the effect of vaccination on coronary heart disease.