COVID‐19 breakthrough infections and hospitalizations among vaccinated patients with dementia in the United States between December 2020 and August 2021

INTRODUCTION: There is lack of data on COVID‐19 breakthrough infections in vaccinated patients with dementia in the United States. METHODS: This is a retrospective cohort study of 262,847 vaccinated older adults (age 73.8 ± 6.81 years old) between December 2020 and August 2021. RESULTS: Among the fully vaccinated patients with dementia, the overall risk of COVID‐19 breakthrough infections ranged from 8.6% to 12.4%. Patients with dementia were at increased risk for breakthrough infections compared with patients without dementia, with the highest odds for patients with Lewy body dementia (LBD) (adjusted odds ratio or AOR: 3.06, 95% confidence interval or CI [1.45 to 6.66]), followed by vascular dementia (VD) (AOR: 1.99, 95% CI [1.42 to 2.80]), Alzheimer's disease (AD) (1.53, 95% CI [1.22 to 1.92]), and mild cognitive impairment (MCI) (AOR: 1.78, 95% CI [1.51 to 2.11]). The incidence rate of breakthrough infections among fully vaccinated patients with dementia increased since December 2020 and accelerated after May 2021. The overall risk for hospitalization after breakthrough infections in patients with dementia was 39.5% for AD, 46.2% for VD, and 30.4% for MCI. DISCUSSION: These results highlight the need to continuously monitor breakthrough severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infections and outcomes in vaccinated patients with dementia.