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By Felix Rogers, DO
Years ago, a patient was telling me about her symptoms when her twin sister interrupted her: “would you stop telling the doctor that you have the flu? You only have the symptoms of the flu.” At the time, my reaction was to think this was pretty harsh…if it’s mid-winter in Michigan and you’re feeling miserable with a respiratory ailment, does it matter if it’s influenza or just a cold?
Well, yes, it does matter, because the flu is associated with major morbidity and mortality, especially cardiovascular disease if you are over age 65. As we get older, our immune system weakens, even if we enjoy good health. With a decline in the body’s defense system, the risk of catching the flu increases and the risk of flu-related complications increases.
Millions of people in the US catch the flu during the season that begins in October, peaks in December and January and then lasts until spring. Over the past decade the disease caused about 35,000 deaths and 225,000 hospitalizations annually. If there is a year with a sudden change in the virus or an outbreak that affects a large unvaccinated population, as happened in 2017-2018, these numbers can increase dramatically. That season, there were nearly 80,000 deaths and 950,000 hospitalizations.
By comparison, over the last 50 years, cardiovascular disease (CVD) is the leading cause of death among men and women in the US, causing about 800,000 deaths each year. Advancing age is the most powerful risk factor, but more than 60% of patients with CVD are under age 65. In the group of patients between 55 and 64 years, more than half of men and women have some manifestation of CVD.
The most common cause of cardiovascular disease is hardening of the arteries (atherosclerosis). Besides the well-known cholesterol build-up in the blood vessels, this is a progressive and chronic condition characterized by inflammation and by abnormalities in blood clotting. The disease process of influenza causes intense inflammatory changes and clotting disorders, with changes in pre-existing atherosclerotic plaque that are identical to those seen with a heart attack. This greatly increases the risk of acute myocardial infarction, heart failure and stroke in people with pre-existing CVD; a 2018 study published in the New England Journal of Medicine reported that the risk of a heart attack increases 6-fold during the first week of flu symptoms.
Vaccination against influenza is not just useful to protect against the flu and its respiratory complications — it is an important treatment to protect against cardiovascular disease including heart attacks, heart failure, cardiac arrest and stroke. The risk of heart attack and stroke falls by about 50% after vaccination.
Every person older than 65 who has any manifestation of cardiovascular disease is recommended to receive the high dose flu vaccine, which is four times stronger than the standard vaccine. Although this high dose carries with it a small increased chance of more discomfort at the injection site and a higher risk of headache and malaise, it confers a significant additional benefit in terms of protecting against cardiac complications from the flu: the relative incidence of the flu is reduced by 25% compared to the standard dose.
This “adult- strength” flu vaccine has been developed for use in all people greater than 65 years of age, whether or not they have cardiovascular disease. Flu shots have not been shown to reduce the risk of heart attacks in people under age 65 who do not have evidence of cardiovascular disease, but the dramatic decrease in flu-related illness justifies its use as a public health measure.
Felix is a cardiologist with the Henry Ford Health System