A large US claims-based study found that adults aged 65 and older who received a high-dose flu vaccine had a lower observed risk of Alzheimer dementia than those who received a standard-dose vaccine, with the association lasting up to 25 months in per-protocol analyses and 28 months in intention-to-treat analyses. The signal appeared stronger and more sustained in women, though the authors stress that the findings are observational and need confirmation in longer prospective studies.