From article https://www.ox.ac.uk/news/2025-06-25-how-do-vaccines-reduce-...

> 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.

Link to study https://www.nature.com/articles/s41541-025-01172-3

I don't know if this study changes the conclusion that Shingrix is more affective than Zostavax.

I haven't yet seen that result asserted, but maybe others have.