Long COVID may now be less common than previously thought
CBC
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Long COVID can be a severely debilitating condition for those who live with it, but the growing list of symptoms and conflicting estimates on how often it occurs make it incredibly difficult to measure exactly how many people it affects.
Post-COVID-19 condition, as it's called by the World Health Organization (WHO), is also not an inevitability for most people who get infected and it now appears significantly less common than earlier research suggested — thanks in part to vaccination.
Based on data from the early in the pandemic, the WHO estimates placed the condition at a rate of between 10 to 20 per cent of COVID-19 patients, while the Public Health Agency of Canada (PHAC) states it can occur in between 30 to 40 per cent of those not hospitalized.
Canada's Chief Public Health Officer Dr. Theresa Tam went as far as to say back in May that long COVID can affect up to 50 per cent of all patients, adding that the symptoms can be "quite broad and non-specific."
But with estimates that more than half of Canadians have been infected with COVID since December after the emergence of Omicron and its highly contagious subvariants, there is a lack of evidence to suggest there are currently millions of COVID long haulers in Canada.
Newer research suggests long COVID is occurring at a much lower rate than estimates from early in the pandemic, before widespread vaccination. PHAC is now working to better understand the true number of cases — while acknowledging their data is outdated.
"Long COVID is real. There are a lot of people suffering from it," said Bill Hanage, an epidemiologist at Harvard University's T.H. Chan School of Public Health in Boston.
"But you don't serve those people by pretending that 40 per cent of the population is in that boat. In my view, it's actually a bit disrespectful to the people who are genuinely suffering from long COVID to pretend that that is the case."
Many of the estimates cited by health organizations are based on early data that largely looked at patients in 2020, long before COVID-19 vaccines and Omicron dramatically changed the immunity landscape in Canada and around the world.
One study published in The Lancet in July 2021, cited by PHAC as one of its main sources for its estimate that 30 to 40 per cent of non-hospitalized patients develop long COVID, looked at fewer than 1,000 patients between April 2020 and December 2020.
"I assume that due to vaccination and the Omicron variant, fewer people will now be affected by long COVID," Clara Lehmann, a lead author of the study and professor at the department of Internal Medicine at the University of Cologne in Germany, said in a recent email.
PHAC also cites two systematic reviews as evidence for its high estimates of long COVID — a preprint study authored by its researchers from late 2021 that has not yet been peer reviewed, and a study in The Journal of Infectious Diseases from April.
Many of the papers analyzed in the studies are from before the emergence of Omicron and COVID-19 vaccines, while a significant proportion also had no control groups from the general population to compare against. The lead author of The Lancet study PHAC cited also said she expected the rate to be much lower.
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