Objectives: To: 1) evaluate the effectiveness of COVID-19 vaccines among South Asians living in Ontario, Canada compared to non-South Asians, and 2) compare the odds of symptomatic COVID-19 infection and related hospitalizations and deaths among non-vaccinated South Asians and non-South Asians. Design: Test negative design study Setting: Ontario, Canada between Dec 14, 2020 and Nov 15, 2021 Participants: All eligible individuals >18 years with symptoms of COVID-19 and subdivided by South Asian ethnicity versus other, and those who were vaccinated versus non-vaccinated. Main Outcome measures: The primary outcome was vaccine effectiveness as defined by COVID-19 infections, hospitalizations, and deaths, and secondary outcome was the odds of COVID-19 infections, hospitalizations, and death comparing non-vaccinated South Asians to non-vaccinated non-South Asians. Results: 883,155 individuals were included. Among South Asians, two doses of COVID-19 vaccine prevented 93.8% (95% CI 93.2, 94.4) of COVID-19 infections and 97.5% (95% CI 95.2, 98.6) of hospitalizations and deaths. Among non-South Asians, vaccines prevented 86.6% (CI 86.3, 86.9) of COVID-19 infections and 93.1% (CI 92.2, 93.8) of hospitalizations and deaths. Non-vaccinated South Asians had higher odds of symptomatic SARS-CoV-2 infection compared to non-vaccinated non-South Asians (OR 2.35, 95% CI 2.3, 2.4), regardless of their immigration status. Conclusions: COVID-19 vaccines are effective in preventing infections, hospitalizations and deaths among South Asians living in Canada. The observation that non-vaccinated South Asians have higher odds of symptomatic COVID-19 infection warrants further investigation.

Dr. Anand holds a Canada Research Chair in Ethnic Diversity and Cardiovascular Disease, and the Michael G DeGroote Heart and Stroke Foundation of Canada Chair in Population Health Research. Dr. Loeb sits on Vaccine advisory boards for Seqirus, Pfizer, Sanofi, Medicago, GSK, Merck, Noravax; DSMB for CanSino Biologics. Dr Shah is funded by the University of Toronto as the Novo Nordisk Research Chair in Equitable Care of Diabetes and Related Conditions. Other authors declare that they have no competing interests.

This study received funding from the COVID-19 Immune Task Force through the Public Health Agency of Canada. This study was also supported by ICES, which is funded by an annual grant from the Ontario Ministry of Health (MOH) and the Ministry of Long-Term Care (MLTC). This work was also supported by the Ontario Health Data Platform (OHDP), a Province of Ontario initiative to support Ontario's ongoing response to COVID-19 and its related impacts.

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