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Statin drugs, taken by about 28 percent of U.S. adults over 40, may interfere with the effectiveness of flu vaccines, researchers report.
Two studies find that the popular cholesterol-lowering drugs may reduce the body’s immune response to the vaccine in older people, who already have a lowered immune response.
The researchers say their reports are meant to kick off more investigation — not to make people worry about taking statins when they get their flu shots. But they may help explain why flu vaccines often work so poorly among older people.
In one of the studies, a team at Cincinnati Children’s Hospital looked at data from 7,000 people over the age of 65 who got flu vaccines over nine years. Those who took statins produced fewer virus-fighting antibodies after vaccination, they reported in the Journal of Infectious Diseases.
“Apparently, statins interfere with the response to influenza vaccine and lower the immune response, and this would seem to also result in a lower effectiveness of influenza vaccines,” said Dr. Steven Black, who led the study.
“Apparently, statins interfere with the response to influenza vaccine and lower the immune response."
Statins are used by 48 percent of the U.S. population over the age of 75, according to the Centers for Disease Control and Prevention. They include drugs with brand names such as Lipitor, Mevacor, Crestor and Zocor.
A second team reviewed the cases of nearly 140,000 people enrolled in a large managed care organization in Georgia. They found those who took statins were less protected from serious respiratory disease than those who didn’t after getting a flu shot.
“If you are on statins, the effectiveness of flu vaccine is somewhat lower,” said Dr. Saad Omer of Emory University, who led the Georgia study.
“Our findings may explain only partially why a flu vaccine is somewhat less than perfect in the elderly. There are several other reasons and one of them being that our immune system becomes somewhat less effective as we age. So that’s one chunk of factors that may influence less than optimal responses in the elderly associated with flu vaccine.”
The researchers stress that it’s far too soon to assume that the statins are directly to blame. There may be something else different about people who take statin drugs, which prevent heart attacks and stroke.
“The studies indicate that older people and males who are taking statins have a less good response to the influenza vaccine. It is not a huge effect but it is notable,” said Dr. William Schaffner, an infectious disease specialist at Vanderbilt Medical School and a spokesman for the National Foundation for Infectious Diseases.
“Our findings may explain only partially why a flu vaccine is somewhat less than perfect in the elderly."
“It makes it even more important that the research continues to develop better influenza vaccines.”
In the meantime, doctors say, there are now high-dose flu vaccines available for people over 65, which do seem to boost the immune response.
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And studies have shown that if more people in a community are vaccinated against flu, that can help protect the elderly, who are by far the most likely to die from flu.
The Centers for Disease Control and Prevention recommends that just about everybody get vaccinated against flu, freshly each year because the immunity wears off and because the flu virus mutates.
In any given year flu kills between 3,000 and 49,000 people, and 80 to 90 percent of them are over 65.