Commonly used vaccines may also protect against dementia, according to a recent paper published in the Journal of Alzheimer’s Disease [J. Alzheimer’s Disease 2023; 95(2): 703–718)].
The authors found that after receiving the tetanus/diphtheria vaccine and whooping cough (aka, pertussis) vaccine there was a 30% reduction in the risk of developing AD. Similar results were observed in individuals who received the pneumococcal vaccine. In the case of the vaccine for herpes the risk was reduced by 25%.
“The question not answered by the study is: what is the mechanism whereby the vaccine would protect against dementia?,” asks Domenico Praticò, M.D., FCPP, and Director of the Alzheimer’s Center at Temple. Praticò was not directly involved in the study.
“For years, there was empirical observation suggesting that activation of our immune system could keep Alzheimer's disease at bay. Interestingly, some previous small studies on the effect of general vaccinations on dementia risk provided somewhat promising results,” Praticò says.
In the current study, the authors looked at a large number of subjects (>200,000) who received some or all of the common vaccines recommended by the Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP) for older adults: tetanus, diphtheria (with and without pertussis), herpes, and pneumococcus. This group was compared with a group of individuals who did not receive any vaccines.
“A possible answer to this important biological question is that the vaccines, by “instructing” the immune system to respond to a particular target could indirectly “prepare” the immune cells to respond more efficiently to any hypothetical insult to the brain,” suggests Praticò. “In other words, they may be better prepared for modulation of the inflammatory response (aka neuroinflammation) within the central nervous system, and regulate inflammation only for the beneficial aspects it provides.”
“The current study would support some recent epidemiological observations that exposure to infectious agents (e.g., herpes) is garnering attention as a possible additional risk factor,” adds Praticò, “in addition to the already known risk factors for AD, such as genetics, diet, and age.“
“In summary, this new study is compelling,” Praticò concludes, “however; it needs to be replicated to strengthen the findings and the potential translational value. Moreover, the hypothesis regarding the possible mechanism needs to be tested both in animal models as well as in vitro (cells) models.”
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Domenico Pratico
Scott Richards North Star Charitable Foundation Chair for Alzheimer’s Research, Founding Director and Professor at Alzheimer's Center at Temple, Professor of Neural Sciences
Alzheimer's Center at Temple University Lewis Katz School of Medicine
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