Physicians' Academy for Cardiovascular Education

Influenza vaccination lowers CVD risk

Literature - Udell JA, et al. JAMA Oct 2013 - JAMA. 2013;310:1711-1720.


Association Between Influenza Vaccination and Cardiovascular Outcomes in High-Risk Patients

A Meta-analysis
 
Udell JA, Zawi R, Bhatt DL, et al.
JAMA. 2013;310:1711-1720.
 

Background

As winter, and the flu season, is coming, there remains interest in a potential association between respiratory tract infections, of which influenza and influenza-like illnesses are common causes, [1,2] and subsequent cardiovascular events.[3-9] Seasonal influenza-like illnesses may explain a major determinant of the timing of acute thrombotic vascular events in patients with previously stable coronary artery disease (CAD) and cerebrovascular disease.[3]
Accumulating data suggest that an annual influenza vaccination can protect against cardiovascular disease events, particularly in high-risk individuals with existing coronary heart disease. [4,10-19]
Medical association guidelines recommend universal vaccination in patients with, or at risk of, cardiovascular disease for protection from general influenza complications, largely based on observational findings.
This study is a systematic review and meta-analysis of six randomized, controlled clinical trials of influenza vaccine studying cardiovascular events as efficacy or safety outcomes.
The trials analyzed covered 6,735 patients (mean age, 67 years; 51.3% women; 36.2% with cardiac history; mean follow-up time, 7.9 years). The primary endpoint was a composite of major adverse CV events, including CV death or hospitalization for MI, unstable angina, stroke, HF and urgent coronary revascularization within 12 months of follow-up. The secondary endpoint was CV mortality and other individual CV events within 12 months of follow-up.
 

Main results

  • People who received the flu vaccine had a significantly lower risk of cardiovascular events.
  • Influenza vaccination was associated with a 36% lower risk of cardiovascular events: cardiovascular events occurred in 2.9% of people in the vaccination group versus 4.7% of controls (RR 0.64, CI 0.48-0.86, P =0 .003).
  • 58 people would need to be vaccinated to prevent 1 major cardiovascular event.
  • The protective effect was largely restricted to people who had had a recent acute coronary syndrome (ACS): the influenza vaccine was associated with 55% lower risk of major adverse cardiovascular events in patients with a recent acute coronary syndrome (ACS)
  • RR for patients with recent ACS: 0.45 [95% CI, 0.32-0.63]
  • RR for patients without recent ACS: 0.94 [95% CI, 0.55-1.61] recent ACS (P for interaction =0.02).
  • In ACS patients, eight patients would need to be treated with the influenza vaccine to prevent one major cardiovascular event.
  • Results were similar with the addition of unpublished data.
 

Conclusion

In this meta-analysis, influenza vaccination was associated with a lower risk of major adverse cardiovascular events within 1 year, particularly in patients with recent ACS. Future research with an adequately powered multicenter trial to confirm the efficacy of this low-cost, annual, safe, easily administered, and well-tolerated therapy to reduce cardiovascular risk beyond current therapies is warranted.
 

Editorial comment (20)

More than half of people under the age of 65, and as many as one-third of people over the age of 65, don’t receive annual flu vaccines. One of the most consistent and relevant findings of operational research is that recommendation for vaccination from physicians and other health care professionals is a strong predictor of vaccine acceptance and receipt among patients… all health care practitioners can therefore recommend influenza vaccine to their patients.
 
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