Flu, pneumococcal vaccines may prevent Alzheimer’s disease

Regular influenza and pneumococcal vaccinations may help stave off the development of Alzheimer’s disease (AD), according to two studies presented at AAIC 2020.

In the first study, researchers propensity score matched data from the US-based Cerner Health Fact EHR database to establish a cohort of 4,146 patients with AD (1,992 and 2,154 who had and had not received influenza vaccination, respectively) and 4,940 individuals without AD (2,551 and 2,389 who had and had not received influenza vaccination, respectively).

In the general population, receipt of influenza vaccine was associated with a 17 percent reduced risk of AD (odds ratio [OR], 0.8309; p<0.0001). In addition, increasing frequency of influenza vaccinations (≥1 per year) was tied to a decreasing risk of AD compared with less frequent vaccination (OR, 0.87; p=0.0342). [AAIC 2020, Poster presentation; Theme: Public Health]

Time to event analysis showed that younger age at first influenza vaccination may lead to a smaller risk of AD (hazard ratio, 1.0924 per 1-year increase in age at first vaccination; p<0.001).

In adults aged 75–84 years, consistent influenza vaccination led to a 5.79 percent reduction in AD risk for 16 years.

“A lack of disease modifying treatments for AD has focused efforts towards prevention or delaying onset,” said study author Albert Amran, a medical student at McGovern Medical School at The University of Texas Health Science Center, Houston, Texas, US, and co-authors.

“[I]nfluenza vaccination, increased frequency of administration, and earlier age of vaccination were demonstrated to reduce the incidence of AD. [It was also suggested] that influenza vaccination reduced the likelihood of AD development over a 16-year period and ameliorated the additional risk conferred by comorbid health conditions such as diabetes,” said Amran. “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.”  

While modulation of neuroinflammation via vaccination was a proposed mechanism behind the observed effect, further research is needed to identify the actual mechanism, he said.

Pneumococcal vaccination may play a role

Another study of 5,146 individuals enrolled in the Cardiovascular Health Study showed that individuals who received pneumococcal vaccinations at age 65–75 years had a reduced risk of AD after age 75 years.

After adjusting for sex, race, birth cohort, education, smoking, and number of G alleles, individuals who received a pneumococcal vaccine between age 65 and 75 years had a reduced risk of AD after age 75 years compared with non-recipients (OR, 0.70; p=0.04). [AAIC 2020, Poster presentation; Theme: Basic Science and Pathogenesis]

Increasing number of pneumococcal vaccinations only (OR, 0.88; p=0.03) and both pneumococcal and influenza vaccinations (OR, 0.88; p=0.01) was also tied to a reduced risk of AD after age 75 years, though increasing number of influenza vaccinations only had no impact (OR, 0.94; p=0.10).

The greatest effect exerted by pneumococcal vaccinations only appeared to be among individuals who were not carriers of the rs2075650 G allele, a genetic risk factor for AD (OR, 0.62; p=0.04), though the benefits were seen with increasing number of pneumococcal vaccinations only (OR, 0.85; p=0.05), influenza vaccinations only (OR, 0.89; p=0.02), and both pneumococcal and influenza vaccinations (OR, 0.85; p=0.03) in this subgroup.

“Accumulating evidence suggests that infections may be important contributors to AD. In this light, repurposing of existing vaccines that show beneficial effects on morbidity and mortality beyond the protection against target disease might be a promising new approach to AD prevention,” said study author Associate Professor Svetlana Ukraintseva from the Duke University Social Science Research Institute, Durham, North Carolina, US, and co-authors. 

“Vaccinations against pneumonia before age 75 may reduce Alzheimer’s risk later in life, depending on individual genotype. These data suggest that pneumococcal vaccine may be a promising candidate for personalized Alzheimer’s prevention, particularly in non-carriers of certain risk genes,” she said.

What’s next?

“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,” commented Dr Maria Carrillo, chief science officer of the Alzheimer’s Association, who was not affiliated with the study.

“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. 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,” she noted.