Hundreds of thousands of Quebecers have contracted variant Omicron in the last few months. After a lull, cases now appear to be on the rise once more in the province as the BA.2 subvariant becomes increasingly dominant. What are the chances of getting reinfected? The duty discuss with experts.
The BA.2 version of Omicron now accounts for almost half of the cases of COVID-19 identified in Quebec, according to the latest report from Public Health. This would be transmitted 30 to 50% faster than its predecessor.
Since the start of the pandemic, three million Quebecers have been infected with COVID-19. Quebec considers that a person is “adequately protected” from the risk of reinfection for a period of three months following contracting the virus. Benoît Barbeau, virologist and professor in the department of biological sciences at the University of Quebec in Montreal, explains that there is a possibility of being reinfected during this period.
“If you have been infected with Omicron, there are chances of being infected with Delta or BA.2,” he says. Three sub-variants of Omicron would have developed since as far as the first months of 2021, underlines the expert. “There’s BA.1, which is what we call the Omicron variant. There is BA.2, which we are currently undergoing. And another one called BA.3, which doesn’t seem as competitive as the others,” he explains.
The two sub-variants are related, but they are different because they have had time to evolve over time, change and diverge. “Do not think that Omicron, which generated the previous wave, gave rise to BA.2. They were created at the same point of origin,” he says. “They are different enough that the chances of being reinfected are not zero, especially if the antibodies have had time to decrease,” he adds.
What would be the chances of contracting BA.2 tomorrow morning if, for example, someone caught Omicron a few months ago? The state of scientific knowledge is not yet clear, but Benoît Barbeau estimates that a person has a 20 or 30% risk of being infected once more with the BA.2 subvariant.
Another study from Qatar suggests that a person who has caught Omicron has a 5 to 12% risk of being reinfected with BA.2 following a month and a half, points out the Dr Donald Vinh, microbiologist-infectiologist at the MUHC. “It’s a high rate,” he said.
Pierre Talbot, professor at the Center Armand-Frappier Santé Biotechnologies of the INRS, affirms for his part that the same type of immunity develops with BA.1 and BA.2 “The immune system has an immunological memory, therefore immunity will reactivate if it sees a similar virus once more, it says. It is unlikely to re-infect one of the two sub-variants”.
However, there are still gray areas, underlines the Dr Donald Vinh, because it is difficult to know if someone contracted Delta or Omicron in December, for example, as the two strains were circulating at the time. “If we have not been infected with Omicron but rather with Delta, there is a high risk of catching [un sous-variant], he said. People who have not been infected with BA.1 are at risk of having it this time around, and they can get sick.”
What virulence?
Lionel Berthoux, professor of virology and infectious diseases in the department of medical biology at the University of Quebec at Trois-Rivières (UQTR), warns once morest what is considered a three-month period of immunity.
“In reality, two weeks following an infection or a vaccine, we have a level of immunity at its maximum and, then, it will gradually decrease over the months. It goes down faster following a vaccine than following a natural infection, he says. But there is no magic date before which we would be completely protected. It does not work like that at all and it is a bad message that Public Health is sending ”.
Someone can be exposed to the virus once more but the risks of complications are low, he thinks. According to him, the immunity of people who have already been infected with BA.1 will remain good. “The BA.2 sub-variant is not going to make as big a wave as that of December and January” last, he believes.
Data on the virulence of BA.2 are not yet clear, but it would not be more dangerous than Omicron. “The majority of studies indicate that it is not associated with more serious symptoms, mentions Benoît Barbeau. There’s even a study that suggested it might be less dangerous.”
According to him, there is a “certain immunity” in Quebec, considering the vaccination coverage and the number of people who have been infected. “It will definitely give us a hand once morest BA.2,” he said. This can protect once morest the risk of infection and hospitalization, he believes, while adding that one should avoid being too lax in measures to protect once morest COVID-19.
The Dr Donald Vinh, however, tempers that a three-dose vaccination coverage of 52% in the province is not high. He adds that you also have to take into consideration when the person had their last dose. “If someone had a third dose four months ago, the immunity may have waned and the person may be at risk,” he thinks.
According to Benoît Barbeau, one should not think that the variants or sub-variants will continue to be less virulent in the future, or that they will be equivalent to Omicron. “There is a chance that the next one might be more dangerous, warns Benoît Barbeau. We must remain vigilant”.
