At this point in the pandemic, you have likely had COVID-19 at least once. Maybe twice. maybe even three times, as some unlucky Canadians have experiencedall while this virus evolved to become ever more adept at infecting us.
It is clear that reinfections of this coronavirus are the norm, just like those behind the common cold. Unfortunately, that also means that initial speculation about single episodes of COVID-19 offering immunity against future infections has gone out the window.
What is more confusing is how often you can get infected with SARS-CoV-2 and whether future infections will always be milder than the first, as the virus finds a way to enter our bodies again and again.
Reassuringly, scientists say that for most healthy adults, including those with added protection from vaccination, COVID-19 infections should become easier to manage as their immune systems get repeated training in how to handle this virus. particular pathogen.
“Your first COVID infection will probably be, not invariably but probably, your worst,” said Dr. Allison McGeer, an infectious disease specialist and professor at the University of Toronto Dalla Lana School of Public Health.
“And then as you get more and more exposed, you get better and better protections.”
Coronaviruses attack repeatedly
After months or even years of avoiding the virus altogether, it may come as a surprise that COVID-19 can affect you more than once.
Early in the pandemic, some scientists expressed hope for herd immunity: If enough people contracted or were vaccinated against COVID-19, herd immunity against infection would reach a threshold where the virus would be unable to find new human hosts. .
Unfortunately, that’s not easy with a coronavirus.
First identified in humans in the 1960s, viruses in this family have likely attacked us repeatedly for centuries. SARS-CoV-2 is just the newest kid on the block.
“Four of those other family members cause about 30 percent of our common colds and routinely reinfect us,” said Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore.
“We’ve all had multiple episodes of other coronavirus infections, and that’s where this virus has always been headed. So reinfections are not something to be surprised about.”
However, they were rare during the early part of the pandemic. SARS-CoV-2 is hitting people again and again at this point, two and a half years later, in part because we’re giving it the chance.
“This would have happened much more frequently if we hadn’t all stayed home and kept our distance,” McGeer said. “It is not that the virus is doing something different than it would have done before; it’s that we’re behaving differently.”
Add in increasingly contagious variants that are able to evade the front-line soldiers of our immune systems, and you have a recipe for reinfections on a more regular basis. What is not clear is how often this virus will strike.
Four long-studied seasonal human coronaviruses appear capable of reinfecting people every 12 months, according to research published in Nature Medicine which involved scientists tracking a group of healthy adults for more than 35 years.
But unlike that seasonal pattern, SARS-CoV-2 remains erratic, more of a constant roller coaster ride than a big rise and fall in any given year.
In Canada and many other countries, a seventh wave is now underway, fueled by another immune-evasive Omicron sub-variant, BA.5. It occurs in the summer months, well before the typical cold and flu season, and not long after previous waves driven by other members of the Omicron family tree.
McGeer, like many close COVID watchers, is still unsure what path this virus will take in the long term.
“Are we probably going to settle into winter activity? Yes, eventually, but maybe not for another year or two,” he said. “Are you sure we will? Nope.”
Reinfections are usually no worse than the first.
What several experts who spoke to CBC News are more certain of is that subsequent COVID-19 infections should feel milder than the first. That doesn’t necessarily mean a walk in the park, but at least not as rough as your body’s first encounter with this virus.
“From all the literature I’ve seen, when reinfections are happening with increasing frequency, they are generally not worse,” said Angela Rasmussen, a virologist with the Organization for Vaccines and Infectious Diseases at the University of Saskatchewan in Saskatoon. “And that’s exactly what you’d expect, because that’s how the immune system works.”
There are a couple of ways to train your immune system to fight this virus faster and smarter. One is directly exposed to SARS-CoV-2, which comes with all the possible health consequences of an infection.
The other is to get vaccinated, which allows your body to learn about this particular pathogen without facing those risks. (Think of that option as a martial arts lesson, rather than scrapping it in a surprise fist fight.)
If you’re vaccinated and contract COVID-19, the virus could still get past your immune system’s first line of defense, your neutralizing antibodies, and sneak into your cells, Rasmussen said.
“Immediately, your memory T cells from your vaccination will say, ‘Wow, I’ve seen that guy before; it’s time to go out there and start killing these cells that are infected,'” he explained.
In other words, a well-trained immune system cannot prevent infection, but it can often control it quickly. That means an invader that might once have wreaked havoc just doesn’t get that chance.
So far, that has been the experience of Erin Wilson, a fitness teacher and actress in Halifax, who recently contracted COVID-19 again after first being infected last December. (She is also vaccinated).
The first round left her exhausted and bedridden for days, “completely incapacitated.” Her next fight was not pleasant, and several days later, she was still battling chest congestion, cough, and fatigue, but she noticed that it was a little easier.
“The second time he didn’t knock me out as much,” Wilson said.
Not all reinfections will be ‘benign’
So if you’ve been through COVID-19 at least once before, should you throw caution to the wind and catch it again and again? Not quite.
The virus does not treat everyone equally, stressed Adalja of Johns Hopkins. “What we’re learning is that not every second or third infection is going to be benign, and that’s going to be particularly true when it comes to higher-risk populations.”
A study focused on US veterans. — who are mostly older men — found that reinfections in that group appeared to have a higher risk of death or hospitalization.
The document, which has not yet been peer-reviewed, made headlines in recent weeks. But several experts, including Adalja, cautioned against reading too much into their early findings, which may not apply to the general population.
However, while repeated infections should feel milder for most healthy people, he said it’s important to be aware of changing risk factors for serious illness.
“Maybe there’s someone who gained a lot of weight and became obese, or developed diabetes in the time that followed, or developed some other condition that puts them at higher risk,” Adalja said. “Maybe they become immunocompromised, all of that will play a factor.”
In the elderly or those who are immunocompromised, medical professionals expect to see a variety of worse outcomes related to serious reinfections, said Dr. Sameer Elsayed, a professor at Western University in London, Ontario, and a consultant in infectious diseases, internal medicine and medical microbiology at the London Health Sciences Center and St. Joseph’s Health Care London.
That could include lung damage caused directly by the virus, he said, to issues such as aggravation of “long-term COVID” symptoms from prior infection or serious secondary bacterial or fungal infections, particularly in those who require admission to an ICU. intensive care.
“This latest example is also similar to asthmatics who may require repeated hospitalizations for something seemingly as simple as a common cold,” Elsayed said. “These repeated infections cause lung damage and can potentially lead to premature death depending on their severity, but we don’t see this in healthy people who continue to have common colds year after year.”
So, as we all face the possibility of repeat COVID-19 infections throughout our lives, your personal risk of severe illness could change over time, and the burden of reinfections from this ever-evolving virus will not be felt. in the same way.