COVID-19 vaccine effectiveness among South Asians in Ontario: A test-negative design population-based case-control study

ObjectivesTo: 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. DesignTest negative design study SettingOntario, Canada between Dec 14, 2020 and Nov 15, 2021 ParticipantsAll 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 measuresThe 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. Results883,155 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. ConclusionsCOVID-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. What is already known?Some ethnic communities, such as South Asians, were disproportionately impacted during the COVID-19 pandemic. However, there are limited data on COVID-19 vaccine efficacy among this high-risk ethnic group. What this study adds?- In this large population-based study including close to 900,000 individuals in Canada, we show COVID-19 vaccines are effective in preventing symptomatic SARS CoV-2 infections, hospitalizations and deaths among both South Asians and non-South Asians. - We also demonstrate that, among non-vaccinated individuals, South Asians have higher odds of COVID-19 infection, and an increased risk of COVID-19 hospitalizations and deaths compared to non-South Asians.