Héma-Québec Seroprevalence Study | More than one in four adults is infected with COVID-19 in winter

More than one in four adults in Quebec contracted COVID-19 during the winter between December and March, according to a new seroprevalence study released Monday by Héma-Québec. This is the agency’s fourth major investigation since the pandemic began two years ago.

Posted at 5:00 am

Henri Ouellette-Vezina

Henri Ouellette-Vezina
The press

Alice Girard bosses

Alice Girard bosses
The press

“We’re not surprised at all. In our personal lives, we have all recently known someone who has contracted Omicron. And it didn’t go under for the first three months of the year,” says the Dright Interviewed by Marc Germain, Vice President of Medical Affairs and Innovation at Héma-Québec The press.

It is exactly 27.8% of adults who contracted the virus during the winter season. During the first wave it was just 2.2%. A new serological study will also be conducted “in the coming weeks” to account for the entire sixth wave powered by the BA.2 variant. “It is already clear that we will be above 30%,” confirms the Dright German.

Essentially, the study, conducted on just over 1,600 blood donors in January, February and March, shows that the Omicron wave is affecting more than a third of people in the greater Montreal area and about a quarter in the regions.

The under-40s in particular contracted the virus in the metropolis during the fifth wave. As many as 70% of people aged 18 to 40 living on the island of Montreal or in its crowns would have contracted it between December and March.

“This is impressive because we’re really talking about evidence of recent infections that occurred during the Omicron wave. And when we talk to our public health colleagues, it doesn’t contradict at all other assessments they make on their side,” explains the Dright Germain on this subject and specifies that the risk of reinfection remains very real.

decrease in blood donations

Aside from these numbers, Héma-Québec reminds us that it’s still hard to bear the effects of the sixth wave of COVID-19.

The organization says it is “struggling to meet its weekly goals due to cancellations.”

Already in early April, almost 20% of blood donations were canceled on certain days, representing an “unusually high” cancellation rate.

“This concern is very real, especially since with daylight saving time – and it was like this even before the pandemic – it’s much more difficult to convince people to take the time and donate blood,” says Dr.right Germain, who calls on those who are able to do so to mobilize to donate blood.

In particular, we encourage users to check availability by stopping by a donation point, even though it theoretically only works by appointment. The organization estimates that every 80 seconds someone in Quebec needs a blood donation. The hospital network requires approximately 1,000 donations per day to meet needs.

A challenge with vaccination

Since the beginning of the pandemic, Héma-Québec has measured participants for the presence of antibodies to protein S present on the surface of SARS-CoV-2. If blood tests showed these antibodies, the person was likely infected with the virus.

“When our body comes into contact with the virus, our immune system develops antibodies against different parts of the virus,” says Dr.right Gaston De Serres, Chief Physician of the Immunization Division of the National Institute of Public Health of Quebec (INSPQ).

However, the situation has become more complicated with the arrival of the vaccine. Since vaccination also leads to the formation of antibodies against protein S, it was then impossible to distinguish antibodies induced by vaccination from those induced by infection. The experts therefore had to select a different target protein. They chose the nucleocapsid because the antibodies it elicits are only present in people who have been infected with the virus.

However, this choice of protein brings with it a new challenge. In fact, the antibodies induced by the nucleocapsid are much less durable than those against the surface protein previously used.

“We can get a good picture of the recent infections, but we have no information on the number of people infected since the beginning of the pandemic,” explains Dr.right From Serres.

Nonetheless, these seroprevalence studies are proving to be very useful for health authorities, argues Dr.right From Serres. “It’s really important because we use it for multiple purposes,” he says.

First, these studies allow the implementation of the best possible vaccination strategies depending on the immunity conferred on the population. The information also confirms the models predicting the evolution of the pandemic. “What we saw with the Omicron wave has been confirmed [l’efficacité de] our models of the development of the pandemic. The ministry, the government and the health authorities can therefore trust our predictions,” he concludes.

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