Fig. 1: Study objectives, study design and flow chart.

^aUnvaccinated individuals were assigned the same index date as their vaccinated matches. ^bDuring the matching process, the following inclusion criteria were applied to unvaccinated comparators based on their assigned index date: no receipt of RZV prior to or within 6 months following the index date, no receipt of ZVL within 6 months following the index date, ≥65 years of age at index date, KPSC member for ≥365 days prior to index date and ≥6 months after index date (allowing for 31-day gap), no dementia diagnosis or dementia medications prescribed prior to or within 6 months of index date, and no death within 6 months following the index date. ^cOnly for the RZV-vaccinated group. ^dIndex date for two-dose RZV-vaccinated recipients was the date of their second RZV dose. For unvaccinated comparators, index date was assigned based on the second RZV dose date of their matched counterpart. EHR electronic health record, HR hazard ratio, HZ herpes zoster, ICD-10 International Classification of Diseases, Tenth Revision, IPTW inverse probability of treatment weighting, KPSC Kaiser Permanente Southern California, m month, MCI mild cognitive impairment, n number, RZV recombinant zoster vaccine, Tdap tetanus, diphtheria and acellular pertussis vaccine, ZVL zoster vaccine live.