Influenza Vaccine Reduces Risk of Alzheimer Disease in Older Adults

Older adults who receive the influenza vaccine are 40% less to develop Alzheimer disease (AD) than individuals who are not vaccinated against influenza, according to new research.

While prior studies have shown a reduced risk of dementia following influenza vaccination in certain populations, no data showed an association between the influenza vaccine and the risk of developing AD.

The patient data eligible for the study—from September 2009 to August 2019—included individuals who were free of dementia during the 6-year pre-study period and were 65 years or older by the start of follow-up.

Propensity-score matching was used to categorize the patients into 2 cohorts of flu-vaccinated and flu-unvaccinated, for a total of 935,887 matched pairs. Additionally, the researchers estimated the relative risk (RR) and absolute risk reduction (ARR) for the effect of influenza vaccination on AD risk during the 4-year follow-up.

Of the flu-vaccinated patients, 5.1% (n = 47,889) had developed AD during the median follow-up of 46 months. Comparatively, 8.5% (n = 79, 630) of the flu-unvaccinated patients had developed AD during the same follow-up period. The researchers reported a RR of 0.60 (95% CI, 0.59 - 0.61) and ARR was 0.034 (95% CI, 0.033 - 0.035), which corresponded to a number needed to treat of 29.4.

“It will be critical for future investigations to clarify which mechanisms underlie the apparent effect of flu vaccination on AD risk, whether age at vaccination moderates the vaccine’s association with AD risk, and whether influenza vaccination also affects rate of progression in patients with [mild cognitive impairment] or AD,” concluded the researchers.


—Jessica Ganga


Bukhbinder AS, Ling Y, Hasan O, et al. Risk of Alzheimer’s disease following influenza vaccination: a claim’s-based cohort study using propensity score matching. J Alzheimers Dis. Published online June 13, 2022. doi:10.3233/JAD-220361