In a cohort study of more than 9000 older adults, receiving a single influenza vaccination was associated with a 17% lower prevalence of AD compared with not receiving the vaccine.
In addition, for those who were vaccinated more than once over the years, there was an additional 13% reduction in AD incidence.
In another study, which included more than 5000 older participants, being vaccinated against pneumonia between the ages of 65 and 75 reduced the risk of developing AD by 30%.
The subject of vaccines “is obviously very topical with the COVID-19 pandemic,” Rebecca M. Edelmayer, PhD, director of scientific engagement for the Alzheimer’s Association, told Medscape Medical News.
“While these are very preliminary data, these studies do suggest that with vaccination against both respiratory illnesses, there is the potential to lower risk for developing cognitive decline and dementia,” said Edelmayer, who was not involved in the research.
The findings of both studies were presented at the Alzheimer’s Association International Conference (AAIC) 2020, which was held online this year because of the COVID-19 pandemic.
Lower AD Prevalence
The influenza vaccine study was presented by Albert Amran, a fourth-year medical student at McGovern Medical School at the University of Texas Health Science Center at Houston.
The researchers used electronic health record data to create a propensity-matched cohort of 9066 vaccinated and unvaccinated adults aged 60 and older.
Influenza vaccination, increased frequency of administration, and younger age at time of vaccination were all associated with reduced incidence of AD, Amran reported.
Being vaccinated for influenza was significantly linked to a lower prevalence of AD (odds ratio [OR], 0.83; P < .0001) in comparison with not being vaccinated. Receiving more than one vaccination over the years was associated with an additional reduction in AD incidence (OR, 0.87; P = .0342).
The protection appeared to be strongest for those who received their first vaccination at a younger age, for example, at age 60 vs 70.
Amran has two theories as to why influenza vaccination may protect the brain. One is that vaccination may aid the immune system as people age.
“As people get older, their immune systems become less able to control infection. We’ve seen this with the ongoing pandemic, with older people at much higher risk for dying. Giving people the vaccine once a year may help keep the immune system in shape,” Amran told Medscape Medical News.
Another theory is that the prevention of influenza itself may be relevant.
“Flu infections can be extremely deadly in older patients. Maybe the results of our study will give another reason for people to get vaccinated,” Amran said.
The other study was presented by Svetlana Ukraintseva, PhD, Duke University, Durham, North Carolina.
The researchers investigated associations between pneumococcal vaccine, with and without an accompanying influenza vaccine, and the risk for AD among 5146 participants in the Cardiovascular Health Study. Covariates included sex, race, birth cohort, education, smoking, and a known genetic risk factor for AD: the rs2075650 G allele in the TOMM40 gene.
In a logistic model with all covariates, vaccination against pneumonia between ages 65 and 75 was significantly associated with reduced risk of developing AD (OR, 0.70; P < .04).
The largest reduction in AD risk (OR, 0.62; P < .04) was among those vaccinated against pneumonia who were noncarriers of the rs2075650 G allele.
Total number of vaccinations against pneumonia and influenza between ages 65 and 75 was also associated with a lower risk for AD (OR, 0.88; P < .01). However, the effect was not evident for the influenza vaccination alone.
“The fact that very different pathogens ― viral, bacterial, fungal ― have been linked to AD indicates a possibility that compromised host immunity may play a role in AD through increasing overall brain’s vulnerability to various microbes,” Ukraintseva told Medscape Medical News.
The current findings support further investigation of pneumococcal vaccine as a “reasonable candidate for repurposing in personalized AD prevention,” she noted.
“These results also support the important role of boosting overall immune robustness/resilience in preventing AD,” Ukraintseva added.
Her group is currently working on confirming the findings in another population.
“Neither study can prove that the benefit is directly related to the vaccine itself, but what they can indicate is that potentially, vaccines are a way to protect your health and brain,” Edelmayer told Medscape Medical News.
In a statement, Maria Carrillo, PhD, chief science officer for the Alzheimer’s Association, noted that more research is needed.
The new data call “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,” Carillo said.
Funding for the influenza vaccine study was provided by the Christopher Sarofim Family Professorship in Biomedical Informatics and Bioengineering, a UT STARs Award, the Cancer Prevention and Research Institute of Texas, and the National Institutes of Health. Funding for the pneumonia study was provided by the National Institute on Aging. Amran, Ukraintseva, Edelmayer, and Carrillo have reported no relevant financial relationships.
Alzheimer’s Association International Conference (AAIC) 2020: Posters 41693 and 46751, presented July 27, 2020.