When the more communicable forms of the virus that causes COVID-19 first began arriving in Canada late last year, they accelerated the rate of infection. Now, case data accumulated in Ontario over several months suggests the disease has grown substantially more dangerous.
The assessment, published Tuesday in the Canadian Medical Association Journal, provides the most in-depth look yet at the changing risk posed by COVID-19 in Canada. And it comes with important implications for those who live without vaccination: namely, the experience of a person who caught COVID-19 last year and was lucky enough to fight the virus with little apparent effect, it There is not a reliable guide as to how the disease might affect anyone in Equal Health today.
“The risks have really clearly changed,” said epidemiology professor David Fisman, who co-authored the study with mathematical modeler Ashley Tuit. Both are based at the Dalla Lana School of Public Health at the University of Toronto.
Why the fourth COVID-19 wave is different
The large-scale study was based on results from more than 212,000 cases in Ontario between February and June of this year. Dr Fisman said the vast amount of data available allowed him and Dr Tuit to control for a variety of variables – including age, gender, vaccination status and unrelated health conditions that could contribute to COVID-19 cases in some. can become more serious. People – to show that the virus has actually become more virulent.
The findings are in line with other studies. They suggest that the versions of the virus that the World Health Organization has identified as “anxiety types” are causing many more severe cases of COVID-19 – and not just because they spread more easily.
Overall, the Ontario study found that people with three types of viruses known as alpha, beta and gamma were 52 percent more likely to be hospitalized, with cases in intensive care 89 percent more likely to occur. , and was 51 percent more likely. To cause death compared to the version of the novel coronavirus to be circulated in 2020. All three share a common mutation associated with increased transmission. Earlier this year, the alpha version was the main driver of the third wave of the pandemic in Canada.
After the delta variant emerged in late spring, the figures became even more dire. Delta now accounts for the vast majority of Canadian cases. Compared to someone who caught COVID-19 in Canada a year ago, a person infected with the delta variant today is 108 percent more likely to end up in hospital, 235 percent more likely to be placed in an ICU, and 133 per person. The probability of dying is high.
Although the study does not include what happened as Delta powered the fourth wave of the pandemic in Canada, it does help explain some of the distinctive features of that wave. For example, even though more than two-thirds of Ontario’s population was fully vaccinated in early September, hospital and ICU cases due to COVID-19 were about three to six times higher than last year.
“The virus has gotten smarter and more dangerous, which means we have to get smarter too,” the magazine’s interim editor-in-chief Kirsten Patrick wrote in an accompanying editorial.
In a follow-up to their study posted online last week and awaiting peer review, Dr. Fisman and Dr. Tuit looked more closely at disease outcomes in different age groups. They found that the relative risk of ending up in hospital with COVID-19 now increased with younger age. In other words, while people of all ages face a greater risk of variations, those who are younger and more able to dodge serious illness are seeing that benefit diminish. The researchers cautioned that the low number of ICU stays and deaths among children with COVID-19 means uncertainty is greater about estimating the level of risk in the youngest children.
Dr. Fisman said one of the findings of the combined studies is that vaccination should not be considered only as a philanthropic option that primarily prevents serious disease from spreading to older and more vulnerable populations.
“It’s a lot about direct security,” he said.
Alison Calvin, an infectious-disease researcher at the University of Saskatchewan’s Vaccines and Infectious Diseases Organization, said the Ontario study is important because it captures a difficult-to-measure aspect of the virus at a time when the pandemic is in transition from its early stages. Was. There is no recognized variant of concern, but there are also no approved vaccines where the vaccine and the variant are interacting and having a profound effect on disease dynamics.
“I think it really drives the importance of variants and getting people vaccinated to prevent new variants from emerging,” said Dr. Calvin, who was not involved in the study.
On Monday, the Saskatchewan facility said that Dr. Calvin has received federal funding to start a new project that will look at risks that vary for vaccine efficacy in vulnerable populations, including the elderly and HIV-positive people. As part of an international year-long project, Dr. Kelvin will analyze antibodies collected from vaccination participants in Canada, Italy and Rwanda.
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