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

> 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.