A newly published study shows that AS01-adjuvanted RSV and shingles vaccines were tied to a lower dementia risk in older adults. I’ve written previously about how the shingles vaccines reduce the risk of dementia, but this study adds the RSV vaccine.

The study also implies that the AS01 adjuvant may be partially responsible for both the vaccines’ link to dementia incidence.

This post will examine the new study and provide further information about the AS01 adjuvant.

All about AS01-adjuvanted RSV and shingles vaccines

Both the RSV vaccine (Arexvy), which prevents respiratory syncytial virus infections, and the shingles vaccine (Shingrix), which prevents herpes zoster (shingles) infections, utilize AS01 as an adjuvant.

AS01 is an adjuvant system developed to boost the immune response to vaccines. It consists of two main components: 3-O-desacyl-4′-monophosphoryl lipid A (MPL) and QS-21, which is derived from the Quillaja saponaria plant. This combination helps to stimulate a stronger and more effective immune response, making it particularly useful in vaccines targeting diseases that may not elicit a robust response on their own. 

RSV and shingles vaccines dementia risk study

In a paper published on 25 June 2025 in npj vaccines, Paul Harrison, BMBCh, DM, University of Oxford, England, and colleagues, evaluated electronic health record (EHR) data for US older adults in the TriNetX network, including 35,938 people who received the AS01 RSV vaccine only, 103,798 people who received the AS01 shingles vaccine only, and 78,658 who received both.

These records were matched with an equal number of people who received the seasonal flu vaccine and neither the shingles nor RSV vaccine. Cohorts were matched for 66 covariates, including sociodemographic factors, comorbidities, history of herpes infection, and history of influenza vaccination.

Here are the key results:

• Compared to the flu vaccine, the AS01-adjuvanted RSV vaccine was associated with a 29% increased time without a dementia diagnosis.
• Compared to the flu vaccine, the AS01-adjuvanted shingles vaccine showed an 18% increased time without a dementia diagnosis.
• Among people who received both vaccines, there was a 37% increase in time without a dementia diagnosis.

Summary

Both the RSV vaccine and the recombinant shingles vaccine contain an AS01 adjuvant to stimulate the immune system; the flu vaccine does not. This may mean that the AS01 adjuvant may affect dementia risk, but more research would be required to confirm this hypothesis.

There is research that certain infections may increase the risk of dementia. So, if the AS01 adjuvant provides a better immune response for the vaccines, then it may better protect against these infections.

Whatever the reason, I think the evidence is growing that being vaccinated against RSV and shingles may delay or prevent the onset of dementia.

Citations

• Roman F, Burny W, Ceregido MA, Laupèze B, Temmerman ST, Warter L, Coccia M. Adjuvant system AS01: from mode of action to effective vaccines. Expert Rev Vaccines. 2024 Jan-Dec;23(1):715-729. doi: 10.1080/14760584.2024.2382725. Epub 2024 Aug 5. PMID: 39042099.
• Taquet M, Todd JA, Harrison PJ. Lower risk of dementia with AS01-adjuvanted vaccination against shingles and respiratory syncytial virus infections. NPJ Vaccines. 2025 Jun 25;10(1):130. doi: 10.1038/s41541-025-01172-3. PMID: 40562756; PMCID: PMC12198376.

Help the Skeptical Raptor keep writing about vaccines

There are four ways you can help contribute to keeping this website running at full speed:

1. GoFundMe.
2. Contributing via Patreon.
3. Buying on Amazon.
4. Sharing this article on Social Media.