What is the risk of reinfection with the Omicron variant of the COVID-19 virus?

Hundreds of thousands of Quebecers have contracted the Omicron variant in recent months. After a lull, cases now appear to be on the rise again in the county, with variant BA.2 becoming increasingly dominant. What are the risks of re-infection? duty Discuss with experts.

The BA.2 version of Omicron now accounts for nearly half of COVID-19 cases identified in Quebec, according to the latest report from Public Health. This will go 30% to 50% faster than the previous one.

Since the beginning of the pandemic, three million Quebecers have contracted COVID-19. Quebec considers a person to be “adequately protected” from the risk of reinfection for three months after contracting the virus. Benoit Barbeau, a virologist and professor in the Department of Biological Sciences at the University of Quebec in Montreal (UQAM), explains that it is possible to re-infection during this period.

“If you have Omicron, you can have Delta or BA.2,” he says. The expert points out that three subtypes of Omicron could have been developed as far back as the early months of 2021.” , which does not look as competitive as the others.”

The two sub-variables are related, but different, as they have had time to evolve, change, and differentiate. “Don’t think it was Omicron, which generated the previous wave, that gave rise to BA.2. It was created at the same point of origin,” he says.

“They are different enough that the risk of infection again is not zero, especially if the antibodies have had time to decline.”

What are the odds that someone who tuned in to Omicron a few months ago will get a BA.2 tomorrow morning? The state of scientific knowledge is not yet clear, but Benoit Barbeau estimates the risk to be 20% or 30%.

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A study from Qatar indicates that a person who has been infected with Omicron has between a 5% and 12% risk of developing BA.2 after a month and a half, confirms Ds Donald Finh, a microbiologist and infectious disease scientist at McGill University Health Center. “It’s a high percentage,” he says.

Pierre Talbot, professor at INRS’s Armand-Frappier Santé Biotechnology Center, asserts for his part that the same type of immunity develops with BA.1 and with BA.2. The immune system has an immune memory, so your immunity will activate if you see a similar virus again. It is unlikely that you will have an infection with either of the two subvariables. »

However, there are still gray areas, emphasizes ds Vinh, because it is unclear whether someone contracted, say, Delta or Omicron in December, as both strains were circulating at that time. “A person who is not infected with Omicron, but rather with Delta, has a high risk of infection [un sous-variant], He said. People who have not had BA.1 are at risk of developing it this time around, and can get sick. »

What virulence?

What is a three-month period of immunity, warns Lionel Bertou, a professor in the fields of virology and infectious diseases in the Department of Medical Biology at the University of Quebec at Trois-Rivieres.

“In fact, two weeks after an infection or a vaccine, we have an immunity level at its maximum, which then will gradually decrease over the months. Immunity wanes faster after vaccination than with a natural infection. But there is no magic date before we will be fully protected.” It doesn’t work like that at all, and it’s a bad message that public health is sending.”

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It is believed that someone could be exposed to the virus again, but the chances of complications are low. According to him, the immunity of people who have already contracted with BA.1 will still be good. He believes that “sub-alternative BA.2 will not make a big wave like the one that happened in December and January.”

Data on the virulence of BA.2 is not yet clear, but it will not be more dangerous than Omicron. The majority of studies indicate that it is not associated with more serious symptoms, states Benoit Barbeau. There is even a study suggesting that it may be less dangerous. »

According to him, there is “certain immunity” in Quebec, given the vaccination coverage and the number of infected people. “It will definitely help us with BA.2,” continues the UQAM professor. He believes it can protect against the risk of infection and hospitalization, while adding that we must avoid too much lax health measures against COVID-19.

considered ds However, Vinh believes that the coverage of the three-dose vaccination, which is 52% in the province, is not high. You also have to take into account when the person last received their dose, he adds. If someone took a third dose four months ago, the immunity may have waned, and the person may be at risk. »

According to Benoit Barbeau, do not think that the following variants and sub-variables will have a virulence equal to or less than that of Omicron. “There are chances that the next will be more dangerous. We must remain vigilant.”

François Legault infected with COVID-19

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