Flu Shot Reduces Venous Clot Risk

AHA: Flu Shot Reduces Venous Clot Risk

By Crystal Phend, Staff Writer, MedPage Today Published: November 09, 2008 Reviewed by Robert Jasmer, MD; Associate Clinical Professor of Medicine, University of California, San Francisco

NEW ORLEANS, Nov. 9 -- Vaccination against the flu may also protect against venous thromboembolism, researchers found. In a case-control study, adults who got their immunizations were 26% less likely to develop venous thromboembolism over the next year, Joseph Emmerich, M.D., Ph.D., of the University Paris Descartes, and colleagues reported at the American Heart Association meeting here. The effect was greatest -- a 48% reduction -- before age 52, they added. The influenza virus increases blood viscosity, while the systemic inflammation caused by such infections can also trigger a thrombotic response, the researchers noted. Dr. Emmerich's group speculated that this might have been the mechanism for the protective effect of influenza vaccination, but they noted that clotting events did not vary by season of the year for vaccinated or unvaccinated patients./.../