Flu and Pneumonia Vaccines Could Help Reduce Alzheimer Disease Dementia Risk

This article, "Influenza, Pneumonia Vaccination May Reduce Alzheimer Disease Risk," was originally published in NeurologyLive.

Influenza and pneumonia vaccinations could help reduce the incidence of Alzheimer disease dementia, according to new findings from a number of studies presented virtually at the Alzheimer’s Association International Conference (AAIC) 2020 annual meeting.

A trio of studies suggest that more frequent flu vaccination was associated with a 13% reduction in the incidence of Alzheimer, while vaccination between the ages of 65 and 75 years was linked to a gene-dependent reduction of Alzheimer by up to 40%.

Additionally, the third study using data from a large clinical database implied that 1 influenza vaccination reduced the incidence of Alzheimer by 17%.

Notably, the work by Janet Janbek, PhD student, Danish Dementia Research Centre, Rigshospitalet, University of Copenhagen, et al. found that mortality risk was twice as high—a 6-fold total increase—for those with dementia after infections compared to those without dementia after infection, which led to a 3-fold increase.

“With the COVID-19 pandemic, vaccines are at the forefront of public health discussions. It is important to explore their benefit in not only protecting against viral or bacterial infection but also improving long-term health outcomes,” said Maria C. Carrillo, PhD, chief science officer, Alzheimer’s Association, in a statement.

“It may turn out to be as simple as if you’re taking care of your health in this way—getting vaccinated—you’re also taking care of yourself in other ways, and these things add up to lower risk of Alzheimer’s and other dementias.”

Janbek and colleagues found, using data from Danish national registries, that the mortality rate ratios (MRRs) for those with dementia was 6.52 (95% CI, 6.43–6.61) times higher post-infection than the reference group.

The MRRs were the highest within the first 30 days of infection in those with dementia and remained elevated compared to those without dementia until 10 years after first infection.

Their registry included 1,496,346 people (12,739,135 person-years), of which 575,260 died during follow-up (82,573 of whom had dementia). Janbek noted in a statement that the study supports the need to assess the relationships and why those with dementia seem to be more greatly impacted.

“Our study suggests that the health care system—as well as relatives of people with dementia—should have increased awareness of people with dementia who get infections, so they get the medical care they need,” Janbek said. “People with dementia require more specialized treatment even when their hospital visits are not directly due to their dementia but to what might appear to be an unrelated infection.”

The work conducted by Albert Amran, medical student, McGovern Medical School, University of Texas Health Science Center, and colleagues, utilized an electronic health record dataset that included patients over the aged 60 years and older, including those with Alzheimer disease (n = 311,424), using propensity score matching to obtain a balanced set of vaccinated and unvaccinated patients (n = 9066).

Then, they used chi-square test, uni-variate analysis, and time-to-event analysis to get their results.

Ultimately, what they found was that an influenza vaccine significantly decreased the prevalence of Alzheimer (odds ratio [OR], 0.8309; P <.0001), and the frequency of influenza vaccination can have a marked impact to prevent the onset of Alzheimer (OR, 0.8736; P = .0342).

As well, Amran et al. found through time-to-event analysis that earlier-age vaccination led to a lower risk for Alzheimer than later-age vaccination (hazard ratio [HR] increased by 1.0924 per 1 year of age at first vaccination; P = .0342).

Those who consistently got annual flu shots decreased their risk, translating to an almost 6% reduction between the ages of 75–84 years.

“Our study suggests that regular use of a very accessible and relatively cheap intervention—the flu shot—may significantly reduce risk of Alzheimer’s dementia. More research is needed to explore the biological mechanism for this effect—why and how it works in the body—which is important as we explore effective preventive therapies for Alzheimer’s,” Amran said in a statement.

Svetlana Ukraintseva, PhD, associate research professor, Biodemography of Aging Research Unit (BARU), Duke University Social Science Research Institute, and team, assessed the associations between Alzheimer and pneumococcal vaccination, with and without a seasonal influenza vaccination, in the third work.

They used a cohort of patients aged 65 years and older (n = 5146) from the Cardiovascular Health Study.

They found that having pneumococcal vaccination between the ages of 65 and 75 years could reduce Alzheimer risk by 25% to 30% after adjusting for confounding factors (OR, 0.70; P <.04).

The total number of vaccinations was also associated with a lower risk of Alzheimer later in life (OR, 0.88; P <.01), though this was not observed with solely the flu vaccine.

Additionally, they assessed the presence of the rs2075650 G allele in the TOMM40 gene, a known genetic risk factor for Alzheimer. The largest reduction of risk—up to 40%—was observed for those who did not carry the allele (OR, 0.62; P <.04).

“This research, while early, calls for further studies in large, diverse clinical trials to inform whether vaccinations as a public health strategy decrease our risk for developing dementia as we age,” Carrillo noted in a statement.