Vaccines and Acute Myocardial Infarction

A case control study¹ examining the possible relationship between the flu vaccine and acute myocardial infarction (MI) was recently published in CMAJ. The study authors looked at data from 78 706 patients in the United Kingdom (16 012 cases and 62 694 controls) who were at least age 40 when a first acute MI was diagnosed.

JCDA Commentary

The aim of the CMAJ study¹ was to investigate a possible association between influenza or pneumococcal vaccination and acute myocardial infarction (MI). The conclusions were that pneumococcal vaccination is not associated with a reduced rate of first acute MI. However, influenza vaccination was associated with a reduced risk of acute MI among patients 40 years of age or over. Having the influenza vaccine within the past year was associated with a 19% reduction in the rate of acute MI. If the vaccine was administered within influenza season it was associated with a 20% reduction. Finally, early vaccination was associated with a 21% reduction of acute MI.

In critically appraising this study using the Critical Appraisal Toolkit for Case Control Studies (United Lincolnshire Hospitals, NHS, United Kingdom) I determined that the study results were valid as they met all 11 criteria fields (e.g. Were the cases recruited in an acceptable way? Was the exposure accurately measured to minimize bias?). Furthermore, the authors demonstrated transparency in their methods of conducting the study and in reporting the statistical analyses.

There are 2 conclusions that dental practitioners can take away from this study. First, health care providers should continue to encourage patients with cardiac risk factors to receive an annual influenza vaccination.² Second, on top of helping to prevent illness from influenza and influenza-like infections, receiving the annual influenza vaccination also demonstrates a protective association for acute MI.

One of the primary roles of infection prevention and control is to encourage preventive behaviours, including vaccination. As health care providers, we can encourage our patients to “get the shot, not the flu.” Among health care providers themselves, compliance for influenza vaccinations among oral health professionals ranges from concordance to indifference (usually resulting in no action), to refusal to receive vaccination. Those who refuse are often adamantly opposed to receiving their annual influenza vaccination. Hopefully, the results in this CMAJ study will provide cause for both health care providers and patients to reconsider personal decisions for refusing annual influenza vaccinations.