Millions of people take drugs called statins to lower their cholesterol levels. But two studies now show that these drugs may reduce the effectiveness of flu vaccines.
Flu shots work by revving up the body's immune response to the viruses that cause influenza. Both studies evaluated the effectiveness of flu vaccines in people who either were or were not taking statins. The results of both studies connect statins to a dampened immune response to flu vaccines and to greater odds of having a respiratory infection during flu season.
In one of the studies, researchers analyzed data on how well more than 5,000 people over age 65 responded to different versions of the flu vaccine during flu seasons in 2008 through 2011 in the United States, Colombia, Panama, and the Philippines. People who did not take statins produced 38% to 67% more antibodies against the flu than people who took statins.
However, because the participants in the study were not randomly assigned to take statins, this diminished effectiveness of the vaccines may be due to other factors.
In the second study, researchers examined rates of respiratory infections linked to the flu from 2002 to 2011 among people 45 and older, all of whom got their healthcare through Kaiser Permanente in Georgia. The effectiveness of the vaccine against these infections was 26.2% for people not on statins, but just 12.6% among those using them.
Because respiratory infections can be caused by other bacteria and viruses, it is possible that not all cases in the study were connected to the flu.
Elderly people are the ones more likely to die or face complications from the flu and are also more likely to be taking statins to prevent potentially fatal heart attacks and strokes. Until more is known about how statins affect vaccines, older patients should remain on their statin medications and still get their flu shot each fall, according to an editorial that accompanied the studies in the in the Journal of Infectious Diseases. The editorial, written by Dr. Robert Atmar, an infectious disease researcher at Baylor College of Medicine in Houston, stressed that people on statins should not stop those drugs and should still get a flu shot.