In a study with nearly 2 million older adults, those who received at least one influenza vaccine were 40% less likely than their non-vaccinated peers to develop Alzheimer’s disease over four years of follow-up, according to a new study from UTHealth Houston.
An early online version of the paper detailing the findings is available in advance of its publication in the Journal of Alzheimer’s Disease in August.
“We found that flu vaccination in older adults reduces the risk of developing Alzheimer’s disease for several years. The strength of this protective effect increased with the number of years that a person received an annual flu vaccine – in other words, the rate of developing Alzheimer’s was lowest among those who consistently received the flu vaccine every year,” said first author Avram S. Bukhbinder, MD. “Future research should assess whether flu vaccination is also associated with the rate of symptom progression in patients who already have Alzheimer’s dementia.”
The study comes two years after UTHealth Houston researchers found a possible link between the flu vaccine and reduced risk of Alzheimer’s disease. This new study analysed a much larger sample than previous research, including 935 887 flu-vaccinated patients and 935 887 non-vaccinated patients.
During four-year follow-up appointments, about 5.1% of flu-vaccinated patients were found to have developed Alzheimer’s disease. Meanwhile, 8.5% of non-vaccinated patients had developed Alzheimer’s disease during follow-up.
These results underscore the strong protective effect of the flu vaccine against Alzheimer’s disease, according to Bukhbinder and Schulz. However, the underlying mechanisms behind this process require further study.
“Since there is evidence that several vaccines may protect from Alzheimer’s disease, we are thinking that it isn’t a specific effect of the flu vaccine,” said Professor Paul. E. Schulz, MD, senior author of the study. “Instead, we believe that the immune system is complex, and some alterations, such as pneumonia, may activate it in a way that makes Alzheimer’s disease worse. But other things that activate the immune system may do so in a different way – one that protects from Alzheimer’s disease. Clearly, we have more to learn about how the immune system worsens or improves outcomes in this disease.”
Past research has uncovered a decreased risk of dementia associated with prior exposure to various adulthood vaccinations, including those for tetanus, polio, and herpes, in addition to the flu vaccine and others.
Additionally, as more time passes since the introduction of the COVID vaccine and longer follow-up data becomes available, Dr Bukhbinder said it seeing if there is a similar link between COVID vaccination and the risk of Alzheimer’s disease.