Cases of SARS-CoV-2 reinfection are increasing worldwide.
Some people get SARS-CoV-2 more than once. If the symptoms of the disease should be less severe over reinfections, experts warn the population of certain health risks.
Your first COVID-19 infection will likely be your worst, says Dr. Allison McGeer, an infectious disease specialist at Mount Sinai Hospital and a professor at the University of Toronto's Dalla Lana School of Public Health.
According to her, the majority of healthy adults, especially those who are vaccinated against the disease, will be able to rely on the ability of their immune system to recognize the virus in order to fight it more effectively during of reinfection.
The more you are exposed to it, the better protection you develop, she says.
Herd immunity against COVID-19 has never been and will never be attainable, according to several experts.
First identified in humans in the 1960s, coronaviruses have likely been making us sick for centuries. SARS-CoV-2 is just the latest to appear.
Four of them cause about 30% of colds and they regularly re-infect us, says Dr. Amesh Adalja, senior researcher at the Johns Hopkins Center for Health Security in Baltimore.
We have all were repeatedly infected with other types of coronavirus and it was towards this phenomenon that [SARS-CoV-2] was going. Reinfections should therefore not surprise us.
Reinfections, although rare at the start of the pandemic, are increasingly frequent due to our behavioral changes brought about by the easing of sanitary measures, explains Dr. Allison McGeer.
This would have happened much more frequently if we hadn't all stayed home and kept our distance, she says.
Add to that new highly contagious variants capable of outwitting our immune defences, and you have the perfect recipe for allowing cases of reinfection to multiply. What is less clear, however, is how often the virus can re-infect a subject.
A study published in the scientific journal Nature Medicine, which followed a group of healthy adults for more than 35 years, revealed that 4 types of coronaviruses appear capable of reinfecting humans every 12 months.
Unlike its big brothers in the coronavirus family, however, SARS-CoV-2 does not appear to follow a seasonal pattern.
Canada, like several other countries, is currently facing a seventh wave of COVID-19, caused by Omicron's BA.5 subvariant. This wave occurs in the height of summer, months before the start of flu season and only shortly after previous waves caused by other Omicron subvariants.
Dr. McGeer, like many of her colleagues, still doesn't know what direction the virus will take in the long term.
“Will it become a winter virus? Probably, but not for another year or two. Is this certain? No. ”
—Dr. Allison McGeer, infectious disease specialist at Mount Sinai Hospital
The experts consulted, however, agree that reinfections with COVID-19 19 should cause less severe symptoms than the first infection.
From all the studies I've looked at, when the frequency of reinfections increases, symptoms don't get worse, says Dr. Angela Rasmussen, a virologist at the University of Saskatchewan.
She explains that immune defenses do not prevent reinfections, but allow the body to fight the virus more easily.
This is exactly what we should expect since this is how the immune system works.
This is what Erin Wilson of Halifax has seen. This sports trainer, vaccinated against COVID-19, recently contracted the virus, having been infected for the first time in December 2021.
Last winter, she spent two days in bed, exhausted and completely incapacitated. But while the second infection wasn't pleasant – Ms. Wilson is still battling a cough and fatigue – it wasn't as bad.
“The second time didn't hit me as hard. »
— Erin Wilson
Experts are still warning people about the risk of complications from COVID-19 reinfections.
We realize that second or third infections will not necessarily be mild, especially for high-risk populations, says Dr. Amesh Adalja.
A study of a group of American veterans, the majority of whom were men, found that cases of reinfection in this group appeared to lead to an increased risk of death or hospitalization.
The study, which has not yet been peer-reviewed, has caused much ink to flow in recent weeks. Experts like Dr. Adalja, however, caution that his preliminary results may not apply to the general population.
However, he points out that changes in an individual's state of health could lead to a more serious form of the disease upon reinfection.
In the meantime, the person could have gained a lot of weight and become obese or have developed diabetes or another medical condition that would put her at risk, he explains.
Dr. Sameer Elsayed, Professor at Western University in London and Consultant in Infectious Diseases, Internal Medicine and Medical Microbiology at London Health Sciences Center and St. Joseph's Health Center London, thinks the elderly or immunocompromised could face a wide range of complications.
They could, for example, suffer damage to their lungs or see a worsening of their post-COVID-19 syndrome, commonly known as long COVID, developed following a previous infection. They could also develop other types of infections caused by bacteria or fungi, especially if they have to be hospitalized in intensive care.
He adds that people with asthma may need to be hospitalized for a simple cold.
These repeated infections damage the lungs and can cause premature death depending on their severity, whereas this does not happen in healthy people who catch colds repeatedly, year after year. year after year, says the expert.
With information from CBC's Lauren Pelley