Obtaining COVID-19 for the second time was considered rare. Now, with the spread of the more portable sub-variant of Omicron BA.2 across the country, reinfections are becoming more common, say experts in immunology and infectious diseases.
Exactly how often is not clear. Testing is limited throughout the country and detailed data on COVID-19, which is publicly available, is also limited.
“There is a shortage of tests that are happening and there is some information that suggests that rapid antigen tests are not as accurate as we had hoped against Omicron,” said Jennifer Homerman, a professor of immunology at the University of Toronto and Canadian Studies. Chair in tissue-specific immunity.
“Spread is a difficult question to answer, but we know there are many viruses.”
The degree of positivity of PCR tests, hospitalization data, and wastewater data in many provinces showed increased transmission of the virus.
And data from around the world show that the risk of re-infection is higher with Omicron, experts say.
“When we think about this idea of re-infection, we have to consider that we are still facing a virus that has a unique ability to bypass these early defenses against neutralizing antibodies,” said Jason Kindrachuk, virologist and assistant professor of medical microbiology and infectious diseases. at the University of Manitoba in Winnipeg.
However, cases of re-infection largely do not cause worse symptoms of the disease, said Kindrachuk, who is also the Canadian research chair on the molecular pathogenesis of emerging viruses.
There are many factors that can cause someone to be re-infected with the virus, and researchers are trying to better understand re-infection and what it means during Omicron.
Data from PCR tests in Canada are limited, so many Canadians have turned to rapid tests to see if they have COVID-19. (Jeff Mackintosh / Canadian Press)
Reinfections are on the rise in global data
Data released by Public Health Ontario last week shows that about 11,730 Ontario residents have been re-infected with COVID-19 since November 2020.
According to Ontario health officials, re-infection is when someone has had two laboratory-confirmed cases of SARS-CoV-2 with evidence that they are “separate infections caused by different virus lines.”
South African scientists warned in December that re-infections in people who have already fought COVID-19 appear to be more likely with Omicron than with earlier coronavirus mutants.
A recent increase in re-infections has been seen in parts of the world such as the United Kingdom, which had a similar vaccine in Canada.
Prior to December 6, the proportion of everyday cases in England that were thought to be re-infections was below two percent for nearly six months.
This percentage is estimated to have risen to 9.9% by February, a Reuters analysis of UKHSA data was discovered.
In Italy, a spokesman for the National Institutes of Health said in February that re-infections accounted for about three percent of all infections, up from about 1.5 percent before Omicron.
Why does re-infection occur?
There are many factors why someone has been re-infected with COVID-19, including vaccine status and when a person has been vaccinated or infected, said Dr. Linora Saxinger, an infectious disease specialist at the University of Alberta in Edmonton.
A study in Qatar, published in the New England Journal of Medicine last month, found that recovery from a previous infection was approximately 90 percent effective in preventing re-infection from alpha, beta and delta variants.
Protection against re-infection with the Omicron variant is 60% lower, but “still significant”, the authors said.
Another important aspect of the risk of re-infection is vaccine-induced immunity.
Experts recommend that people make a booster to better protect themselves from COVID-19. (Hannah Bayer / Reuters)
The strength of the immune response will depend in part on a person’s age and overall health. Very old, very young and immunocompromised will have weakened reactions, for example.
That is why the fourth dose is now being distributed to more vulnerable groups across the country.
And although vaccines have repeatedly proven effective in preventing serious illness and hospitalization, Omicron is still “pretty good at puncturing the equivalent of two doses and in many cases, two doses plus infection or three doses,” Saxinger said.
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Antibodies are known to drop over time after someone is vaccinated or infected, said Benoit Barbo, a professor in the Department of Biological Sciences at the Université du Québec à Montréal who studies virology.
“So if you were infected in December or early January, you will already have lower levels of antibodies. This does not mean that you have completely lost your protection against infection, but you will definitely have less protection than you say 10 days after infection, “he said.
The good news is that the immune response generated by vaccination is “strong enough to protect us from a really serious illness and to be in the hospital,” Homerman said.
That’s why experts recommend that people make a booster for this extra protection.
As for the Omicron BA.2 subvariant, early Danish studies suggest that re-infections with this strain appear to be rare.
What do we need to learn?
Barbo said that as parts of Canada and other countries deal with the sixth wave, more data will emerge on who is re-infected and why.
“There will be other options. “The risk of re-infection will always be there,” he said.
But he stressed that the immunity of the population, whether from vaccines or previous infection, is built and allows us to reduce transmission and hospitalization.
All of this is happening as research continues to improve vaccines, whether it’s adapting to new variants or exploring new methods of administering vaccines such as through the nasal cavity, he said.
“It is very important that we continue to improve vaccines.”
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