Flu vaccination early on in the flu season could subsequently significantly reduce the risk of a stroke, a case–control study in UK general practice has suggested.
The study, published in the journal Vaccine, found vaccination reduced the risk of stroke by around a quarter among people who had their flu jab early – between September and mid-November.
However, people who had the flu vaccination later than this had no reduction in stroke risk.
Researchers identified 26,784 cases of stroke and 20,227 cases of TIA from the UK General Practice Research Database between 2001 to 2009, and matched them closely with an equal number of control patients.
They then compared cases and controls’ exposures to flu vaccination in the flu season preceding the date of the case’s stroke.
This revealed flu vaccination given in the same season was associated with a significant 24% reduction in the risk of stroke, after adjusting for a wide range for confounding variables including chronic conditions and cardiovascular risk factors as well as medications and the number of GP consultations.
This was due to a 26% reduction in stroke risk among those who had the vaccination between September and mid-November – there was no reduction in stroke risk from having the flu jab between mid-November and the end of February.
There was also no association between flu vaccination at any time with the risk of TIA.
The team also compared pneumococcal vaccinations between cases and controls, but found no association between having that vaccination and the risk of stroke or TIA.
The researchers, led by Professor Niroshan Siriwardena, professor of primary and prehospital health care at the University of Lincoln, concluded: ‘The finding of an association between reduced risk of stroke with influenza vaccination, but not pneumococcal vaccination, supports the current influenza vaccination programme with the added potential benefit of stroke prevention.
‘This could result in improvements in patient and population health, if the benefit is confirmed by experimental studies and leads to higher vaccination rates.’