Treatment approaches against dementia find exciting potential in vaccines

Treatment approaches against dementia find exciting potential in vaccines

Shingles Vaccine Shows Promise in Reducing Dementia Risk

A recent study published in the journal Nature has found that the herpes zoster (shingles) vaccine could potentially lower the risk of dementia in the general population by as much as 20%. The study, which took advantage of a policy change in Wales, found that those born on or after September 2, 1933, were eligible for the herpes zoster vaccination, while those born before that cutoff date were not.

The researchers found that the vaccine reduced the probability of getting dementia by one-fifth over a seven-year period. This reduction is greater than or comparable to the dementia risk reductions seen with other vaccines, such as the respiratory syncytial virus (RSV) vaccine, and notably higher than with the annual flu vaccine.

Key points supporting this comparison include a large study that found adults receiving two doses of the recombinant zoster vaccine (RZV, Shingrix) had a 33% lower risk of dementia versus unvaccinated controls. Another large UK Biobank study reported a 32% lower risk of dementia with shingles vaccine recipients, independent of APOE-e4 genetic risk. An observational US study showed that Shingrix recipients had an 18% reduced risk of dementia compared to those who only received the flu vaccine, while the RSV vaccine was associated with an even larger 29% reduction.

Meta-analyses and cohort studies report consistent findings of 15-35% lower dementia risk with shingles vaccines (both Zostavax® and Shingrix®), with protective effects persisting after adjusting for confounders. In contrast, the flu vaccine, though widely recommended, is not observed to lower dementia risk as significantly as the shingles vaccine or RSV vaccine.

Possible mechanistic explanations for the shingles vaccine’s dementia risk reduction include immune system stimulation via the AS01 adjuvant (found in Shingrix and RSV vaccines), reduction of neuroinflammation, prevention of viral reactivation in the brain, and nonspecific immune-related neuroprotection. This adjuvant effect is less prominent or absent in many other vaccines like the flu vaccine.

Limitations of the study include the fact that most studies are observational and cannot prove causality. Research is ongoing to clarify mechanisms and confirm long-term protective effects. The study did not differentiate between different types of dementia, such as dementia due to Alzheimer's disease or dementia due to stroke.

The study raises provocative questions about how vaccines work and how our immune system can potentially prevent dementia. The study design allowed researchers to compare two groups without actively depriving any one group of access to vaccination. The study suggests that vaccines may have a broader role in experimental therapeutics outside the realm of infectious diseases.

The World Health Organization estimates that vaccines prevent between 3 million and 5 million deaths annually from diseases like diphtheria, tetanus, influenza, measles, and COVID-19. Vaccines may open the door to other breakthroughs in understanding and treating degenerative disorders of the brain. The study did not differentiate between different types of dementia, such as dementia due to Alzheimer's disease or dementia due to stroke. There is a possibility that the vaccine may have conferred protection by activating the immune system and providing "trained immunity." Studies based on health records suggest that past exposure to viruses increases the risk of dementia, while routine vaccines reduce the risk.

In conclusion, among studied vaccines, the herpes zoster vaccine, especially RZV, shows one of the strongest and most consistent associations with reduced dementia risk, outperforming the flu vaccine and comparable to or slightly less than the RSV vaccine in this regard. Prospective studies that specifically test how giving a vaccine changes the risk for future dementia may benefit from studying patient populations with specific types of dementia.

1. The herpes zoster (shingles) vaccine, particularly the recombinant zoster vaccine (RZV, Shingrix), has shown a 33% lower risk of dementia in adults compared to unvaccinated controls, according to a large study.
2. The annual flu vaccine is not observed to lower dementia risk as significantly as the shingles vaccine or the respiratory syncytial virus (RSV) vaccine, according to meta-analyses and cohort studies.
3. The study on shingles vaccine and dementia risk has raised questions about the potential role of vaccines in preventing degenerative disorders of the brain, such as dementia and Alzheimer's disease.
4. The World Health Organization estimates that vaccines like those for diseases such as COVID-19 can prevent between 3 million and 5 million deaths annually.
5. While research is still ongoing, the study on the shingles vaccine and dementia risk has highlighted the potential role of AIs (adjuvants) like the one found in Shingrix and the RSV vaccine in reducing neuroinflammation and preventing viral reactivation in the brain, promoting mental health and health-and-wellness.
6. Studies based on health records suggest that past exposure to viruses increases the risk of dementia, while routine vaccines reduce the risk, implying a possible relationship between immune system activation and mental health.

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