Dr Zahid Asghar recently attended the North American Primary Care Research Group (NAPCRG) conference in New York City to present findings from ‘Influenza vaccination and risk of stroke: self-controlled case-series study’. This was an observational study of investigating the association between influenza vaccination and stroke led by Professor Niro Siriwardena, director of CaHRU, and Dr Carol Coupland, associate professor in statistics at the University of Nottingham.
The study involved analysis of almost 18 thousand cases of stroke over a period of eight years from a general practice database, the Clinical Practice Research Datalink. The investigators found a significant reduction in risk of stroke up to 59 days following vaccination. The work follows publication of a case-control study earlier this year and involving almost 10,000 patients showing a 20% reduction in risk of stroke associated with flu vaccination together with previous studies conducted by Professor Siriwardena and his team showing a reduction in risk of heart attack associated with influenza vaccine.
It is not known how influenza vaccination prevents heart attack or stroke. It might be because influenza has been shown to occur two to four weeks before these conditions and may trigger them in a proportion of cases or it might be due to immunological protection from the vaccine. There was worldwide interest in this area of research following the team’s study published in the Canadian Medical Association Journal.