Clinical question
Does influenza vaccination reduce the risk of cardiovascular (CV) events?
Bottom line
For every 100 patients vaccinated for influenza within about 1 month of an acute coronary syndrome (ACS), 2 fewer will experience CV events and 2 fewer will die at 1 year compared with placebo. The impact of influenza vaccination in primary CV prevention and other CV conditions is less clear.
Evidence
At least 6 meta-analyses compared the effect of influenza vaccination to placebo or no vaccination on CV events.1 This article focuses on the most complete systematic review.2 Results are statistically significant unless noted.
Secondary prevention (5 RCTs; N=4187)2: Vaccination reduced risk of all-cause death (relative risk reduction [RRR] of about 45%) and CV events (RRR of about 35%).
- The highest-quality, largest (N=2532), multi-country RCT3 compared 1-time vaccination versus placebo 3 or fewer days after myocardial infarction (MI). At 1 year:
— Death: 2.9% versus 4.9% with placebo.
— Cardiovascular events (death, MI, stent thrombosis): 5.3% versus 7.2% with placebo.
— Local injection site reactions: About 5% absolute increase.
- Limitations: Cardiovascular benefit is seen only in patients with recent ACS (unclear benefit in stable coronary artery disease) in subgroup analysis.2
Heart failure (RCT; N=5129)4: Vaccination did not reduce death or CV events compared with placebo at 2 years, but reduced overall hospitalization (15% vs 18% with placebo).
Primary prevention5: No difference in CV deaths based on 12 events in 2 RCTs, and no other CV events reported.
No difference in CV events with different vaccine types or doses,6 or with timing (administration during MI hospitalization or within 30 days of discharge).7
Context
Recent respiratory tract infections or influenza are associated with increased risk of CV events.8
Cardiovascular guidelines recommend influenza vaccination for people with coronary disease.9
About 40% of Canadian adults with a chronic condition receive annual influenza vaccination.10
Influenza vaccination efficacy for secondary CV prevention is comparable to that of other preventive therapies in reducing recurrent CV events (eg, acetylsalicylic acid and statins [RRR of about 25%]).11,12
Implementation
Patients with ACS should be offered the influenza vaccine. In 1 trial, vaccination within 30 days of discharge had similar effectiveness to vaccination during MI hospitalization,7 suggesting an opportunity for administration by primary care clinicians. People may be more receptive to influenza vaccination when it is recommended by their family physician13 and when potential CV benefits are communicated.14
Notes
Tools for Practice articles in CFP are adapted from peer-reviewed articles at http://www.toolsforpractice.ca and summarize practice-changing medical evidence for primary care. Coordinated by Dr G. Michael Allan and Dr Adrienne J. Lindblad, articles are developed by the Patients, Experience, Evidence, Research (PEER) team and supported by the College of Family Physicians of Canada and its Alberta, Ontario, and Saskatchewan Chapters. Feedback is welcome at toolsforpractice{at}cfpc.ca.
Footnotes
Competing interests
None declared
- Copyright © 2023 the College of Family Physicians of Canada
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