Double effect: flu vaccination protects against stroke

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MunichAnyone who gets vaccinated against the flu at an early stage lowers their risk of a stroke by a quarter. At first glance, the connection seems surprising.

In fact, we are far from knowing all the mechanisms that cause a stroke: "Classic risk factors such as age, smoking and high blood pressure can only be blamed for half of all cases," says study leader Niro Siriwardena from the University of Lincoln.

A quarter fewer strokes

For the study, the scientists evaluated data from almost 27,000 patients aged 18 and over who had suffered a stroke between September 2001 and August 2009. They compared this with a control group of roughly the same size. The result: For people who had received a flu shot, the risk of stroke fell by 24 percent. However, this only applied if the flu vaccination was given early, namely between September and November. Those who got vaccinated later did not benefit from the stroke protection.

However, the scientists did not find a connection between a pneumococcal vaccination, which protects against pneumonia, and the risk of stroke.

Do respiratory infections favor strokes?

In an earlier study, the team had already found a link between flu vaccination and heart attack risk. “We know that cardiovascular diseases are particularly common during the winter season. This could be related to the increased number of respiratory infections such as flu, ”explains study leader Siriwardena. The mechanisms by which respiratory infections or the flu contribute to the risk of stroke are still unknown.

But there are various hypotheses on this: For example, fever could change the function of the vessels and the flow properties of the blood and increase its tendency to clot. A flu infection could also reduce the stability of the deposits on the inner walls of the vessels. When these so-called plaques crumble, a blood clot easily forms that can clog a vessel. Possible consequences are a stroke or heart attack.

"The results of the study underline the importance of national flu protection programs because they show that they have an additional benefit by reducing the risk of stroke."

Vaccinations for those at risk

In Germany, the flu vaccination is recommended by the Standing Vaccination Commission (STIKO) to people who are particularly at risk. This includes all people over 60 years of age, children and adults with chronic illnesses, residents of retirement and nursing homes, pregnant women from the 2nd trimester of pregnancy and people whose risk of infection is particularly high due to diverse contacts. (cf)

Source: A. Niroshan Siriwardena: Influenza and pneumococcal vaccination and risk of stroke or transient ischaemic attack- Matched case control study. Vaccine, 2014; DOI: 10.1016 / j.vaccine.2014.01.029

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