The arrival of the Omicron variant has exploded the proportion of the population having had COVID-19 in the country, especially in Quebec. Nearly three quarters of Quebecers have contracted the coronavirus to date, show new data from the Task Force on Immunity to COVID-19 (GTIC).
Posted at 5:00 a.m.
“We have just confirmed very clearly that the Omicron wave is more of a tsunami than a wave”, immediately launches the Dr Timothy Evans, Professor in the Faculty of Medicine at McGill University and Director of GTIC. “When you compare with previous waves, it just has nothing to do,” he insists.
This working group has been studying the evolution of the virus in the population since April 2020, at the request of the Trudeau government. Its data is based on the seroprevalence of thousands of Canadians who have donated blood, evaluating their samples for average exposure to the virus.
In its most recent report released on Saturday, that The Press obtained, the GTIC estimates that the increase in seroprevalence during the Omicron wave “corresponds to at least 19.6 million Canadians having been infected between December 15, 2021 and August 15, 2022”.
It is enormous. That’s roughly 80,000 infections a day. Before Omicron, less than 10% of Canadians had been infected in the country.
The Dr Timothy Evans, Professor in the Faculty of Medicine at McGill University and Director of GTIC
Overall, infection-acquired seroprevalence in Canada indeed “increased significantly between August 2021 and August 2022, from 5.1% before the Delta wave to 62.5% at the end of August 2022, after about eight months with Omicron variants in circulation”, summarize the experts of the GTIC.
All provinces, and all ages
According to the report, all Canadian provinces have seen their HIV rates soar. In Quebec, it reached 73.7% at the end of August, while in Alberta it was 60%, in British Columbia 52%, in Ontario 55.7%. Even Atlantic Canada, which had maintained lower rates in 2021, is now at just over 60%.
All things considered, the rate of increase in infections in the east of the country was therefore “much higher than in the other provinces and territories during the Omicron phase”, note the specialists.
Young adults, aged 17 to 24, are most affected by the virus, with around 77% of them having been infected. However, this proportion tends to decrease with age: among 25-39 year olds, the proportion reaches 69%, then 60% among 40-59 year olds and 44% among people aged 60 and over.
“Young people weren’t as vaccinated, admittedly, but older people also seemed much more likely to take precautions to prevent infection. We must not forget that there are many older people who have not been infected so far. With the long COVID and all that entails, it will be very important that these people continue to protect themselves. The authorities must continue to send messages in this direction, ”says Mr. Evans.
“Hybrid Immunity”
In his eyes, it will also become crucial in the long term to “clearly grasp the history of immunity in each individual”, or “the number of vaccines, but also the number of infections”. “All of this creates what is called hybrid immunity, and it will be important to define it to determine the best time to receive a booster dose, for example,” explains the professor from McGill University.
About 98% of the blood donors who participated in the study had the IgG antibody “Antispike” in them, which means that they received at least one vaccine against COVID-19. The Dr Evans assures, however, that the vaccination of the subjects had no influence on the data.
“We do two tests: one for Antispike, an antibody generated following vaccination, and another with Anti-nucleocapsid, which is only increased if there has been an infection. It is with this second antibody only that we measure the level of transmission, ”explains the expert.
He notes, however, that blood donors may not be representative of the general population in terms of vaccination coverage, “mainly because children and adolescents are excluded from donating blood”. In May, a Héma-Québec seroprevalence study revealed that one in four Quebec adults had contracted COVID-19 during the winter, between December and March. It was then the fourth major investigation by the Quebec organization since the start of the pandemic.