Recent studies have shown convincingly that vaccines against shingles (Herpes zoster) reduce the risk of dementia. The shingles vaccine now in widespread use (Shingrix) has more of an effect than the previous one (Zostavax). A key difference between these vaccines is that Shingrix contains an ‘adjuvant’, an ingredient designed to enhance the vaccine’s effect. It is therefore possible that the adjuvant contributes to Shingrix’ greater effect than Zostavax on reducing dementia.
The new study, supported by the National Institute for Health and Care Research (NIHR) Oxford Health Biomedical Research Centre (OH BRC) supports this possibility. Researchers analysed the health records of over 430,000 people in the USA in the TriNetX network. They found that the Arexvy vaccine - which protects against respiratory syncytial virus (RSV), a common virus that causes cold-like symptoms - was also linked to a significantly lower risk of developing dementia. Arexvy, now offered to adults over 60, contains the same adjuvant as Shingrix. Both vaccines were similarly effective in reducing dementia risk compared to the flu vaccine (which does not contain the adjuvant); in the 18 months following receipt of Arexvy there was a 29% reduction in diagnoses of dementia. These findings held true across a range of additional analyses and were similar in men and women.