For the second time this year, Justin Trudeau announced this week that he had tested positive for COVID-19. The Prime Minister is the embodiment of a reality that awaits us all: we can be reinfected by SARS-COV-2, the virus that causes COVID-19. And, obviously, we will be.
Posted at 1:00 p.m.
“If we draw parallels with other viruses, for example influenza, we risk having several SARS-COV-2 infections during our lifetime,” says Jesse Papenburg, pediatric infectiologist, microbiologist and epidemiologist. at the Montreal Children’s Hospital.
Why can we re-infect? Mainly for three reasons, according to the Dr Papenburg.
First, some people have not developed sufficient immunity to the first infection, either because they are immunocompromised or simply by bad luck; then, the antibody level decreases over the months (protection is better in the first three to six months); finally, viruses evolve over time.
PHOTO ROBERT SKINNER, THE PRESS
The Dr Jesse Papenburg, pediatric infectious disease specialist, microbiologist and epidemiologist at the Montreal Children’s Hospital
Since March 2020, SARS-COV-2 has been arriving in successive waves, constantly threatening the population with a new variant. Experts expect, however, that the epidemiology will change, and that periods of risk will become less frequent in the future.
“Theoretically, someone can be affected in each wave if the variant changes a lot,” says Dr.r Bruce Mazer, Associate Scientific Director Strategy of the COVID-19 Immunity Task Force and Professor of Pediatrics at McGill University. “But I think a frequency of infection every two or three years would be more in line with our expectations for an endemic virus. »
some protection
It is unclear exactly how SARS-COV-2 will assess or how immune systems will respond in the long term. But according to epidemiologist Jesse Papenburg, the example of the H3N2 influenza can give us some clues about what awaits us.
The H3N2 virus caused a pandemic in 1968, causing more than 1 million deaths. Fifty years later, it is still one of the sources of influenza responsible for seasonal epidemics, hitting vulnerable people harder, but causing far fewer deaths than in 1968. Why? Because the population has developed enough immunity.
With COVID-19, we realize that, even if the risk of reinfection increases over time, we still have some protection against hospitalization and severe infections.
The Dr Jesse Papenburg, pediatric infectious disease specialist, microbiologist and epidemiologist at the Montreal Children’s Hospital
This is the memory response: the immune cells remember the pathogen, thanks to vaccination, first, but also thanks to infections with similar variants.
PHOTO FRANÇOIS ROY, THE PRESS
Benoit Barbeau, virologist, professor in the department of biological sciences at UQAM
“Yes, you have a good chance of reinfecting yourself, but that does not mean that you will have more serious symptoms, on the contrary”, summarizes for his part the virologist Benoit Barbeau, professor in the department of biological sciences of UQAM. .
Studies suggest that hybrid immunity – the combination of a primary series of vaccination and infection – appears to offer the best protection.
No guarantee
According to the most recent data, 40% of Canadian adults have contracted the Omicron variant. Because the population was widely vaccinated and because Omicron is less virulent, the vast majority of those infected escaped without severe or prolonged symptoms.
If you are part of this happy majority, you may have the pleasant impression that you will never suffer from a more serious COVID-19. “I would like to say that it will be the case, but it will really depend on the mutations”, answers the Dr Bruce Mazer of McGill.
The Omicron variant suggests that we are in a general trend where the virus is becoming less and less pathogenic, “but nothing is certain”, recalls virologist Benoit Barbeau, who also draws a parallel with influenza, whose some seasons are more severe than others.
At the population level, the Dr Jesse Papenburg believes we are heading for less and less severe COVID-19 infections, “but on an individual level, having had a mild COVID experience is not a guarantee that the next COVID infection will be so light.” There is still a risk of serious illness, even in people who have been vaccinated and have had an infection before.
Next fall, when we should see an increase in cases, vaccines more suited to the variants that are circulating should also be offered. Do not hesitate to take advantage of it, believes the Dr Mazer. “During this wave of Omicron, mortality is much lower than before and vaccination has played a very important role,” he says.
COVID long
Vaccinated people have an 8% risk of suffering from COVID lasting at least a month, according to British data published this spring and based on the Omicron variant. Does this mean that we run this risk each time we contract COVID-19? The trajectory of the percentage risk of having long COVID is unknown, but it is possible that it decreases from one infection to another, estimates virologist Benoit Barbeau.
Cumulative effect?
In the most severe cases of long-lasting COVID, the SARS-COV-2 virus can cause damage to the heart, lungs, brain, and blood vessels. Can successive infections have a cumulative effect? Again, there is no indication that this will be the case. According to the Dr Bruce Mazer, associate scientific director of the COVID-19 Immunity Task Force’s strategy and professor of pediatrics at McGill University, the effect could be cumulative in frail people who have not had time to heal between the two infections. “It’s something you see for all infections, not just COVID-19,” he says.