What 2 new studies reveal about prolonged COVID in Canada | CBC News

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Two new large-scale reports provide a clearer picture of the long-term impacts of COVID-19 infections on Canadians and the health care system.

A report, released Monday by Canada Statisticsfound that nearly 15 percent of people who have contracted COVID-19 say they experienced persistent symptoms such as fatigue, shortness of breath, or mental confusion three months or more after initial infection.

But compared to earlier phases of the pandemic, the report found that a much smaller proportion of those infected since the Omicron variant arrived in Canada late last year reported long-term symptoms.

StatsCan, which conducted the survey in partnership with the Public Health Agency of Canada, describes it as the first nationally representative report of its kind.

A separate study also published Monday, in the Journal of the Canadian Medical Association (CMAJ), found that people who tested positive for COVID-19 in Ontario used more hospital and health care resources in the months after the infection was cleared than those who tested negative.

The reports are the latest in a growing body of research on the extent of prolonged COVID, an umbrella term for a variety of post-infection health effects.

Among adults who contracted COVID-19 before the Omicron wave hit, nearly 26 per cent told Statistics Canada they had symptoms at least three months after infection. Among those infected as of December 2021, that number dropped to 10.5 percent. (Ben Nelms/CBC)

Fewer people report prolonged COVID from Omicron: survey

The World Health Organization has estimated that what it calls “post-COVID-19 condition” affects 10 to 20 percent of those infected, but those figures are based on earlier phases of the pandemic. More recent research suggests long COVID is now occurring at a much slower rate.

StatsCan says its data suggests some 1.4 million Canadian adults, or about five percent of the total population, experienced symptoms three months after a COVID infection. The survey was conducted among Canadians who had tested positive for COVID-19 or suspected they had the disease.

“This is a significant number of people affected by prolonged COVID,” said Dr. Fahad Razak, an internal medicine specialist and epidemiologist at St. Michael’s Hospital in Toronto, and former head of the COVID-19 Scientific Advisory Board at Ontario.

“Physicians in Canada’s research community have been eagerly awaiting the results of this and the data tells us that we are like other countries,” Razak, who was not directly involved in the study, said in an interview with CBC News.

Because the survey data is based on people’s self-reports of post-COVID symptoms and not compared to a control group of uninfected people, Razak and other doctors said the results should be interpreted with some caution. .

The StatsCan report does not indicate how severe people’s post-COVID-19 symptoms were, or whether symptoms abated at any point after three months.

A medical worker wearing a mask holds up a dose of the COVID-19 vaccine at a Vancouver immunization clinic in January 2022.
Doctors say widespread COVID-19 vaccination likely contributed to the lower rate of long-term COVID cases reported by people infected since December 2021, compared with people infected during previous waves of the pandemic. (Ben Nelms/CBC)

The StatsCan survey found that a markedly lower proportion of people infected since the Omicron wave report long-term symptoms, compared to people infected during the first year and a half of the pandemic.

The survey found that 25.8 per cent of Canadian adults who contracted COVID-19 before December 2021 had symptoms at least three months after infection.

Among those whose cases date from December 2021 onwards, 10.5 percent reported symptoms three months or more after infection.

The lower rate of prolonged COVID among infected Canadians since last December is good news, says Dr. Zain Chagla, an infectious disease specialist at Hamilton, who was not involved in the study.

“The people who are really suffering the most are the people who got infected very early in the pandemic,” Chagla said in an interview with CBC News.

Vaccines likely key to lower frequency: doctors

Both Chagla and Razak said the benefit of vaccination is likely a key reason for the lower frequency of long-term COVID cases among people infected over the past year.

The survey also provides additional evidence linking the likelihood of prolonged COVID with the severity of illness when first infected.

Symptoms at least three months after infection were reported by:

  • 36.4% of Canadian adults who rated their initial case of COVID-19 as severe;

  • 15 percent of those who rated their initial case as moderate;

  • 6.3 percent of those who rated their initial case as mild.

An Asian female doctor wearing a lab coat works on a computer in her office.
Dr. Angela Cheung of the University of Toronto Health Network says both studies are important because they increase knowledge about the impact of prolonged COVID in Canada. (University Health Network)

Dr. Angela Cheung, a senior medical scientist at the University of Toronto Health Network, said the figures in the Statistics Canada report are consistent with previous research.

“I’m glad that this survey has been done and that we’re actually trying to control the number of people affected by COVID-19 with persistent symptoms,” he said in an interview.

Findings may help prepare for lawsuit, researchers say

Cheung, who was not involved in either report, also said the CMAJ study released Monday is important in quantifying the increased use of the health care system after a COVID-19 infection.

The study led by researchers from Toronto’s Sunnybrook Research Institute and the nonprofit research agency ICES looked at the health care use of more than 530,000 Ontario residents who were tested for COVID-19 by PCR. before March 31, 2021.

The researchers compared the demographics of those who tested positive and those who tested negative and found “significantly higher rates of health care use” in the period beginning at least eight weeks after a positive test.

The researchers found a 47 percent increase in the average number of days spent in the hospital per year among women who tested positive, and an average 53 percent increase among men.

The researchers said the findings may help the system prepare for the health care demand associated with prolonged COVID.

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