Abstract
BACKGROUND: We previously demonstrated that the mortality rate following COVID-19 infection was higher in the Chinese population and lower in the South Asian population, compared to the general Ontario population. COVID-19 vaccines are effective in protecting against severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-related diseases. Whether vaccination rates and the postvaccination risk of myocarditis and/or pericarditis are similar among ethnic groups is unclear. METHODS: We conducted a population-based, retrospective cohort study using linked health datasets from Ontario to compare COVID-19 vaccination and postvaccination myocarditisand/or pericarditis rates among the Chinese, South Asian, and general populations. Populations were identified using a surname-based algorithm. The cohort was defined on December 1, 2020, coinciding with vaccine availability, and followed until June 30, 2022, for first and second dose. Myocarditis and/or pericarditis hospital admissions and emergency department visits within 42 days postvaccination were analyzed. RESULTS: For the first dose, vaccination uptake was highest in the general population during the first 120 days. Afterwards, the Chinese and South Asian populations had a higher vaccine rate. A similar pattern was observed for the second dose. Postvaccination myocarditis and/or pericarditis rates were lower among the Chinese population (20 per 1,000,000 first doses) and the South Asian population (21 per 1,000,000 first doses), compared to that in the general population (51 per 1,000,000 first doses), with similar findings following the second dose. The standardized morbidity ratios, comparing observed vs expected myocarditis and/or pericarditis rates postvaccination were similar across the study groups. CONCLUSIONS: A time-dependent differential uptake and lower incidence of postvaccination myocarditis and/or pericarditis occurred among the Chinese and South Asian populations, compared to the general population. Our findings help inform the design of future research and health delivery programs.