[Reading Science] "Herpes Zoster Vaccine Has Dementia Prevention Effect"

Stanford Research Team in the US Releases Large-Scale Case Study Results
20% Reduction in Incidence Rate When Vaccinated Under Age 80

"Elderly individuals vaccinated against shingles are less likely to develop dementia." The dementia prevention effect of 'shingles vaccination,' which had only been rumored, has been confirmed through a large-scale case study, drawing attention.

A research team from Stanford University in the United States published these findings last month on the 23rd on the preprint site for health and medical research, medRxiv. The theory that certain viral infections influence the onset of dementia has been a major research topic since the 1990s, when a team from the University of Manchester in the UK discovered the herpes virus in the brains of dementia patients and published related papers.

The Stanford team focused on the shingles vaccination program that began in September 2013 in the Wales region of the UK. From that time, people aged 80 or younger, i.e., those born after September 2, 1933, were targeted for vaccination with the then-developed shingles vaccine (Zostavax). The researchers analyzed health data from 296,603 individuals born between 1925 and 1942. The results showed that about half of the eligible population, those aged 80 or younger, actually received the vaccine within seven years of the program's start. Notably, the dementia incidence in this vaccinated eligible group was 8.5% lower compared to those who were not vaccinated. Considering that only half of the eligible individuals were vaccinated, the team estimated the overall dementia prevention effect to be as high as 19.9%.

The research team views these statistical results as proof of the dementia prevention effect of the shingles vaccine. Professor Pascal Geldsetzer of Stanford University explained, "There is no reason why people who turned 80 in August would have a higher risk of dementia than those who had their birthday in September; the only difference was whether they received the shingles vaccine or not." He added, "Other factors that could influence dementia incidence, such as large-scale screening campaigns, would have affected both vaccinated and unvaccinated groups equally."

Professor Alberto Ascherio of Harvard University, who did not participate in the study, also commented, "This is a very well-founded research result," adding, "While the difference in dementia incidence could be coincidental, the researchers conducted appropriate studies to eliminate other influencing factors." Professor Russ Izaki of the University of Manchester, UK, who first proposed the possible link between dementia and viral infections in 1991, expressed satisfaction, saying, "This study is special in that it eliminated other factors that could explain the reduced dementia risk in the vaccinated group," and "The results are consistent with what we have argued since 1991."

However, some caution against drawing premature conclusions, noting that dementia is a disease that progresses over more than ten years, while the medical data tracked by the research team was limited to four years post-vaccination. They also pointed out that the dementia prevention effect was mainly observed in women, with little difference between vaccinated and unvaccinated men. Above all, although statistically significant, the study does not prove the exact mechanism, which remains a clear limitation.

Nonetheless, the medical community suggests that shingles vaccination may strengthen the immune system, reduce inflammation that damages brain nerves, and consequently lower the incidence of dementia.