Shingles & RSV Vaccines Linked to Lower Dementia Risk: Focus Shifts to Vaccine Adjuvant
Recent research is bolstering the idea that certain vaccines may offer protection against dementia, and the key may not be the disease the vaccine prevents, but how it stimulates the immune system. A study led by Harrison and colleagues, building on previous findings, suggests the AS01 adjuvant system – a component used in both shingles and RSV vaccines – could be responsible for a considerably reduced risk of dementia diagnosis.
Last year’s report sparked two main hypotheses: that preventing shingles directly lowers dementia risk,or that the AS01 adjuvant itself provides neuroprotective benefits. Previous animal studies lent support to the latter. To investigate further,researchers analyzed electronic health records of over 400,000 patients,comparing dementia rates among those vaccinated with the AS01-adjuvanted shingles vaccine,the AS01-adjuvanted RSV vaccine,both,and a control group receiving only the flu vaccine.The study meticulously constructed cohorts – those receiving only shingles, only RSV, both, and the flu vaccine control – and followed patients for up to 18 months, excluding any dementia diagnoses within three months of vaccination to avoid capturing pre-existing, undiagnosed cases.
The results were compelling. patients who received any vaccine utilizing the AS01 adjuvant system demonstrated a lower risk of dementia compared to the flu vaccine group. Using a metric called the ratio of restricted mean time lost (RMTL),where scores below 1.0 indicate reduced risk, those receiving both the RSV and shingles vaccines achieved an RMTL of 0.63. Those vaccinated with only shingles or RSV showed RMTLs of 0.82 and 0.71 respectively.
This suggests the AS01 system itself, rather than simply preventing shingles or RSV, is driving the protective effect. While the exact mechanism remains unknown, researchers propose several possibilities. one is that the vaccines reduce dementia risk by preventing the infections they target – shingles and RSV – as infections are increasingly linked to heightened dementia risk. However, the relatively rapid appearance of the protective effect argues against this description.
Another, more intriguing possibility, centers on the AS01 system’s specific immunological pathways. The system contains monophosphoryl lipid A (MPL), a component known to stimulate toll-like receptor 4 and has shown promise in improving Alzheimer’s pathology in mouse models.
Harrison and his team emphasize that further research is crucial to unravel the complexities of this connection. Their findings highlight the potential for harnessing the power of vaccine adjuvants – substances that boost immune response – as a strategy for preventing not only infectious diseases, but also devastating neurodegenerative conditions like Alzheimer’s disease and other forms of dementia.
