TORONTO -- More than one-quarter of Canadians have an underlying health condition that would increase the possibility of severe COVID-19 symptoms, according to a new study out of the U.K.

Researchers estimated that nearly 27 per cent of people in the country -- or more than nine million Canadians -- have a chronic condition identified as a risk factor for severe infection, including such ailments as cardiovascular disease and diabetes.

About 1.8 million of that group, or roughly five per cent of the population, would require hospitalization if infected, the study said.

While the data suggests that illness would likely be mild for most with underlying health conditions, it also suggests that in the absence of a vaccine and containment measures, the burden on hospitals could worsen. As of June 15, health officials have recorded more than 99,000 COVID-19 infections and more than 8,100 deaths in Canada.

The new modelling study, published in The Lancet Global Health Journal on Monday, used population estimates for 2020 and data from 188 countries compiled in the Global Burden of Diseases, Injuries and Risk Factors Study (GBD) 2017 to develop the estimated figures. 

Globally, the researchers estimated that 1.7 billion people, or 22 per cent of the world population, had health factors that increased the possibility of severe infection, and about 349 million of them would need to be hospitalized if infected. Of those at risk of hospitalization, less than one per cent are under 20 and nearly 20 per cent are 70 and older.

“We hope our estimates will provide useful starting points for designing measures to protect those at increased risk of severe disease,” said Andrew Clark, an associate professor with the London School of Hygiene and Tropical Medicine, in a news release. “This might involve advising people with underlying conditions to adopt social distancing measures appropriate to their level of risk, or (prioritizing) them for vaccination in the future,” he added. 

The estimates are not exhaustive, the news release cautioned, but could serve as a “starting point for policy-makers,” it said. While the research focused on underlying chronic health conditions, it left out some elements considered by many to be contributing risk factors, such as ethnicity and “socioeconomic deprivation,” which are not included in all guidelines. 

The research noted that while regions with younger populations, such as Africa, have fewer people with underlying health conditions than other areas, such as Europe, this information needs to be communicated clearly “to avoid complacency about risk in Africa” since there are compounding factors not reflected in the numbers. 

“The share of the population at increased risk of severe COVID-19 is generally lower in Africa than elsewhere due to much younger country populations, but a much higher proportion of severe cases could be fatal in Africa than elsewhere,” said Clark. 

In a commentary about the new research, a public health professor said an understanding of who is most at risk can provide an opportunity to “target mitigation strategies” and can help dispel the misconception that “everyone is at equal risk of severe illness.”

“As the authors note, it is time to evolve from a one-size-fits-all approach to one that centres on those most at risk,” wrote Nina Schwalbe with the Columbia University Mailman School of Public Health. “This will need to happen at both the individual and community level.”