A growing number of Canadians appear to be getting COVID-19 for a second time, even after recently recovering from a first bout with the Omicron variant.
Several health experts say becoming reinfected has become much more common since Omicron is so different than previous variants. The differences mean having a previous infection doesn’t offer the same level of protection as with previous strains of the virus.
University of Toronto epidemiologist Colin Furness says even the difference between the subvariant BA.2 and the BA.1 Omicron variant is enough to cause reinfection.
“That is to say if you had Omicron you can still get infected with BA.2,” says Furness. “That seems to be the case and that’s disappointing, obviously.”
Public health data suggests up to 10 per cent of infected Canadians who have recently had BA.2 have previously had BA. 1 or an earlier strain of the virus.
“That shows just because you got Omicron once doesn’t mean you’re bulletproof now,” said Saskatchewan’s chief medical officer, Dr. Saqib Shahab.
However, infectious disease expert at Queen’s University, Dr. Gerald Evans says, based on data from Denmark, getting infected with the BA.2 after having had BA.1 is actually relatively uncommon.
“What we know so far is that we infections with BA.2 if you’ve had BA.1 are still very uncommon. But they do occur and they have been documented,” said Dr. Evans.
He added most of the reinfections that have been seen are from people who were previously infected with the Delta or Alpha strains.
“I don’t think people should be overtly worried,” Dr. Evans shared. “But yes, it does happen and it can happen and when we look at who it’s likely to happen to, it’s going to be the kind of people whose immune response to either a previous infection or vaccination is not as good as it is saying a younger, healthier person.”
“The issue of whether BA.1 or BA.2 reinfection is common is still not known, just simply because we haven’t seen that many of them and we’re still trying to get a handle on genomic sequencing,” added the doctor.
Health experts continue to recommend vaccination to ward off severe outcomes if and when infection occurs, urging all Canadians to get their two doses and get their boosters if eligible.
“Even though you got COVID at some point in the past, you can wait anywhere from two weeks to three months to get a booster,” said Shahab.
Ontario Public Health says nearly 12,000 people have gotten COVID-19 twice since November 2020 and health data in Quebec shows there are 32 reinfections for every 1,000 cases.
In its latest Evidence and Risk Assessment report, Public Health Ontario says BA.2 is now the dominant strain in the province, accounting for 54 per cent of all cases as of March 19.
Wastewater surveillance has suggested Ontario is likely seeing somewhere between 100,000 and 120,000 new cases a day.
Hospitalizations in the province are up over 20 per cent since last week and the head of Ontario’s COVID-19 science advisory table says he is concerned that the high rate of community transmission could lead to a shortage of much-needed health workers.
“There’s no way we can ramp up ICU beds, we need to work with what we have, it will be very challenging because of the staff,” said Dr. Peter Juni.