Risk of adverse events and delirium after COVID-19 vaccination in patients living with dementia

ABSTRACT

OBJECTIVES The aim of this study was to compare incidences of adverse events of special interest (AESI) and delirium in three cohorts after COVID-19 vaccination, pre-pandemic and SARS-CoV-2 polymerase chain reaction (PCR) test positive. DESIGN This is a population-based cohort study using electronic medical records linked with vaccination records in Hong Kong. SETTING AND PARTICIPANTS A total of 17,449 older people with dementia received at least one dose of CoronaVac (n=14,719) or BNT162b2 (n=2730) between 23 February 2021 and 31 March 2022. 43,396 pre-pandemic and 3592 SARS-CoV-2 test positive patients were also included in this study. METHODS The incidences of AESI and delirium up to 28 days after vaccination in the vaccinated dementia cohort were compared with the pre-pandemic and SARS-CoV-2 test positive dementia cohorts by calculating incidence rate ratios (IRRs). Patients who received multiple doses were followed up separately for each dose, up to the third dose. RESULTS We did not detect an increased risk of delirium and most AESI following vaccination compared to the pre-pandemic period and those tested positive for SARS-CoV-2. No AESI group nor delirium incidence exceeded 10 per 1000 person-days in vaccinated individuals. CONCLUSIONS AND IMPLICATIONS The findings provide evidence for the safe use of COVID-19 vaccines in older patients with dementia. In the short run, benefit appears to outweigh the harm due to vaccine, however, longer follow-up should be continued to identify remote adverse events.