Study participants aged 40 to 64 who had received a flu shot had a risk of heart attack reduced by 45%.
For middle-aged adults, getting a flu shot may pay added dividends by offering protection against heart attacks as well as seasonal influenza, according to the results of an Australian study
published online on August 21, 2013, in Heart
In order to investigate an association between influenza infection and increased risk of heart attack reported in previous studies, the researchers conducted a case-control study in a tertiary referral hospital and in orthopedic outpatient clinics in Sydney, Australia, during the winters of 2008, 2009, and 2010. Participants were aged 40 or older and were either admitted to the hospital for a heart attack during flu season or were patients of the outpatient clinic who had never had a heart attack before joining the study. Nose and throat swabs and blood samples were taken from all patients at baseline and 4 to 6 weeks after they enrolled in the study. Patients also provided their medical and vaccination history and demographic information. Self-reports of influenza vaccinations were confirmed from hospital or physician records.
Of 559 total patients enrolled in the study, 276 (49.4%) had received the flu vaccine, and vaccination was found to reduce the risk of heart attack by 45% in those aged 40 to 64. On the other hand, 53 participants (9.5%) had recently had the flu. Although 12.4% of heart attack patients had been infected, compared with just 6.7% of control patients, influenza was not significantly associated with an increased risk for heart attack after adjusting for comorbidities. However, those who had recently suffered an acute respiratory tract infection were more than twice as likely to experience a heart attack as those who did not have an infection.
The authors suggest that their findings be used to inform vaccination policy and to make cardiologists more aware of the role infections can play in heart attack risk.
“The role of an expanded vaccination programme for adults over 50â€…years of age, which would capture a significant proportion of people at risk of [acute myocardial infarction], should be explored by further research,” they write. “At the least, clinicians should be aware of influenza and infection as an underlying and poorly diagnosed precipitant or comorbidity in hospitalised patients and of the preventive benefit of influenza vaccine for patients at risk for [acute myocardial infarction].”