Alzheimer’s disease is a neurodegenerative disease that affects over 50 million people worldwide. This figure is expected to triple in the next 30 years. There is no effective treatment for this disease, which deprives millions of seniors of not only their memory but also their independence. What if a simple flu vaccination could kill two birds with one stone and reduce the risk of developing Alzheimer’s?

A study published in 2020 had previously suggested a protective effect of the influenza vaccination against Alzheimer’s disease, with a 13% reduction in risk. Other studies support these results. The latest study, from June 2022, involved 2 million people over 65 years of age, without signs of dementia. This cohort was followed for several years, with 1 million of them being followed for more than four years. Half were vaccinated against influenza and half were not.

Over the follow-up period, 8.5% of unvaccinated seniors developed Alzheimer’s disease compared to only 5.1% of those vaccinated. This represents a 40% reduction! This effect could be explained by the fact that the flu virus causes inflammation, a factor that aggravates neurodegenerative diseases. Avoiding this inflammation would therefore be protective against Alzheimer’s disease. Other hypotheses, such as a stimulation of the brain’s immune cells by the vaccine, are also proposed.

However, beware of jumping to conclusions. Association does not mean cause and effect: it would be premature to say that the flu vaccine protects against Alzheimer’s disease. For example, it is possible that people who follow the recommendations of the health authorities and get the flu vaccine take better care of their health in general and therefore simply have a lower risk of Alzheimer’s disease. Further studies should provide a better understanding of this link and avoid any bias.

Alzheimer’s Bukhbinder, A. S. et al. Risk of Alzheimer’s Disease Following Influenza Vaccination: A Claims-Based Cohort Study Using Propensity Score Matching. J. Alzheimers Dis. Preprint, 1–14 (2022).