People who receive the recombinant shingles vaccine may receive a dementia diagnosis about 164 days later, on average, than those who receive the live attenuated shingles vaccine, with this delay being more pronounced in women.

We analyzed the available evidence and found that 59 studies or assertions suggest people who receive the recombinant shingles vaccine may receive a dementia diagnosis about 164 days later, on average, compared to those who get the live attenuated vaccine. This delay appears to be stronger in women. No studies or assertions in our review contradicted this pattern. The evidence we’ve reviewed so far leans toward a possible difference in timing of dementia diagnosis between the two vaccines, but we cannot say why this might be. The recombinant vaccine is made using a piece of the virus and an immune-boosting ingredient, while the live attenuated version uses a weakened form of the virus. We don’t know if the difference in how these vaccines work relates to brain health, or if other factors—like age, health habits, or access to care—played a role. The data does not show that one vaccine prevents dementia, only that diagnosis timing may differ slightly. We also note that these findings come from 59 assertions, not clinical trials designed to test dementia outcomes. That means the results could be influenced by how data was collected or grouped. We don’t have enough detail to rule out other explanations. What this means for you: If you’re choosing between shingles vaccines, this possible delay in dementia diagnosis is one of many factors to consider. It’s not a reason to pick one over the other on its own, but it may be worth discussing with your doctor if you’re concerned about brain health. More research is needed to understand whether this pattern holds and what it might mean.