Risk of Adverse Events and Delirium after COVID-19 Vaccination in Patients Living with Dementia

Edmund C.L. Cheung, Miriam T.Y. Leung, Kailin Chen, Eric Yuk Fai Wan, Xue Li, Francisco T.T. Lai, Carlos K.H. Wong, Xiwen Simon Qin, Esther W. Chan, Kui Kai Lau, Hao Luo, Chia Chin Lin, Ian C.K. Wong, Celine S.L. Chui

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)


Objectives: The aim of this study was to compare incidences of adverse events of special interest (AESI) and delirium in 3 cohorts: after COVID-19 vaccination, prepandemic, 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 1 dose of CoronaVac (n = 14,719) or BNT162b2 (n = 2730) between February 23, 2021, and March 31, 2022. Moreover, 43,396 prepandemic 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 prepandemic 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 prepandemic 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.

Original languageEnglish
Pages (from-to)892-900.e12
JournalJournal of the American Medical Directors Association
Issue number6
Publication statusPublished - Jun 2023
Externally publishedYes


  • COVID-19 vaccine
  • adverse events
  • delirium
  • dementia
  • vaccine safety

ASJC Scopus subject areas

  • General Nursing
  • Health Policy
  • Geriatrics and Gerontology


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