In a new study published in Nature Scientific Reports, supported by a Ted Rogers Centre Innovation Fund grant, collaborators sought to understand if public health efforts helped reduce the risk of SARS-CoV-2 infection among those whose sociodemographics and health conditions made them more vulnerable. 

The focus was Ontario, with a large population, tremendous diversity, and a robust system of population data in place courtesy of ICES. 

The Challenge

In the pandemic’s early days, there was a lack of evidence around what put patients at higher risk for COVID-19. In this study, researchers sought local data to gain context on what were true, adjusted risk factors for infection. 

“We were also curious to see, during the peak of the first wave, how non-pharmaceutical public health interventions such as masking were influencing risk among different communities,” says University of Toronto MD/PhD candidate Bahar Behrouzi and a lead author on the paper. “We suspected that these interventions weren’t helping everyone equitably.” 

The study was among the world’s most rigorous to assess COVID-19’s impact at the level of race, ethnicity, and other socioeconomic determinants of health. What we would learn in the first few months of the pandemic yields important lessons for the future.

The Study

Ontario entered a province-wide lockdown after the first wave of COVID-19 peaked in April 2020. Researchers found that, initially, the following clusters of people had the highest infection rates:

  • Older adults
  • Men
  • Immigrants
  • Those with hypertension and diabetes
  • Those living in the most ethnically diverse urban areas
  • Those living in the most socioeconomically disadvantaged communities

After the initial COVID-19 surge, the link between age and infection risk reversed toward younger adults. But all other risk factors persisted throughout 2020, most notably in the communities with the greatest degrees of racial or ethnic diversity.

“After the first-wave peak, interventions such as masks, social distancing and stay-at-home orders reduced infection rates overall, but it was striking to see how much less of an impact they had in neighbourhoods with higher proportions of visible minorities,” says Bahar, who also earned a Ted Rogers Centre Education Fund award for her work. 

Not everyone, as we know, is able to shelter in place or work from home.

What it Means

While it became apparent as the pandemic wore on that these neighbourhoods were not being equitably protected from COVID-19, this study shows that the disparity happened right at the very beginning. 

“You’d tend to expect everyone would reap the benefits of universal measures to curb the spread of COVID-19, but this study helps highlight that is simply not the case,” Bahar says. “What we can learn is that for the next health crisis, we need solutions built from an equitable standpoint, perhaps improved sick day policies and better access to testing in more vulnerable communities.”

By assessing what actually happened in Ontario when SARS-CoV-2 struck, we can take action and develop proactive plans to ensure that the most vulnerable people are as safe as anyone – and build a more resilient health system in the process.


Collaborating researchers on the study are from: ICES, Women’s College Hospital, U of T’s Institute of Health Policy, Management, and Evaluation, U of T Medicine, UHN, St. Michael’s Hospital, Canadian VIGOUR Centre, University of Alberta, Western University of Health Sciences (Pomona, CA), and Sunnybrook.