Flu Shot Linked to Lower Risk of Cardiovascular Events
Wed, 10/23/2013 - 10:03am

Receiving an influenza vaccination was associated with a lower risk of
major adverse cardiovascular events such as heart failure or
hospitalization for heart attack, with the greatest treatment effect
seen among patients with recent acute coronary syndrome (ACS; such as
heart attack or unstable angina), according to a meta-analysis published
in the Journal of the American Medical Association (JAMA).

“Among nontraditional cardiovascular risk factors, there remains
interest in a potential association between respiratory tract
infections, of which influenza and influenza-like illnesses are common
causes, and subsequent cardiovascular events,” according to background
information in the article. Several epidemiological studies have
suggested a strong inverse relationship between influenza vaccination
and the risk of fatal and nonfatal cardiovascular events.

Jacob Udell, of the University of Toronto, and colleagues conducted a
meta-analysis of all randomized clinical trials (RCTs) of influenza
vaccine that studied cardiovascular events as efficacy or safety
outcomes to determine if influenza vaccination is associated with
prevention of cardiovascular events. The researchers identified five
published and one unpublished RCTs of 6,735 patients (average age, 67
years; 51 percent women; 36 percent with a cardiac history; average
follow-up time, 7.9 months) that met inclusion criteria for the study.
Analyses were stratified by subgroups of patients with and without a
history of acute coronary syndrome (ACS) within one year of randomization.

In the five published RCTs, 95 of 3,238 patients treated with influenza
vaccine (2.9 percent) developed a major adverse cardiovascular event
compared with 151 of 3,231 patients (4.7 percent) treated with placebo
or control within one year of follow-up, an absolute risk difference
favoring flu vaccine of 1.74 percent. The addition of the unpublished
data did not materially change the results (2.9 percent influenza
vaccine vs. 4.6 percent placebo or control).

In a subgroup analysis of three RCTs of patients with pre-existing
coronary artery disease (CAD), the risk of major adverse cardiovascular
events among patients with a history of recent ACS was especially lower
with vaccine (10.3 percent influenza vaccine vs. 23.1 percent placebo or
control), an absolute-risk difference of 12.9 percent, compared to
patients with stable CAD (6.9 percent influenza vaccine vs. 7.4 percent
placebo or control). Results were similar with the addition of
unpublished data.

“Within this global meta-analysis of RCTs that studied patients with
high cardiovascular risk, influenza vaccination was associated with a
lower risk of major adverse cardiovascular events within one year.
Influenza vaccination was particularly associated with cardiovascular
prevention 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,”
the authors conclude.

Date: October 22, 2013
Source: JAMA

http://tinyurl.com/kbp9z7a