More contagious BA.2 sub-variant spreading in Canada, complicating opening plans
The highly contagious Omicron sub-variant known as BA.2 is gaining a foothold in Canada just as provinces begin removing pandemic restrictions, according to newly released data.
“Our multi-scale investigations suggest that the risk of BA.2 for global health is potentially higher than BA.1."
A more contagious Omicron sub-variant known as BA.2 could complicate reopening plans now underway in most provinces. GETTY IMAGES
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The highly contagious Omicron sub-variant known as BA.2 is gaining a foothold in Canada just as provinces begin removing pandemic restrictions, according to newly released data.
The spread of BA.2, which is believed to be 1.4 times as contagious as the already highly transmissible original Omicron sub-variant, could complicate reopening plans now underway in most provinces.
As it becomes dominant in the coming weeks, BA.2 could extend the current wave of the pandemic, increase case counts, or slow the decrease in cases at a time when provinces are dropping gathering restrictions and mask mandates.
Experts say it will have an influence on case counts in Ontario, but will likely not be a complete game changer. The Omicron wave is receding, booster rates are relatively high and some 3.5 million people were infected with COVID-19 during the intense Omicron wave that began in December, meaning there is widespread immunity.
Sarah Otto, a professor of evolutionary virology and mathematical modelling at the University of British Columbia, and a leading Canadian expert on BA.2, said its rise in Canada “does not necessarily mean a second major Omicron wave will happen, more likely we’ll see a prolonged peak or a shoulder in the Omicron wave.”
But scientists are watching it closely because there remains so much uncertainty about it and because it has been associated with a renewed spike in cases in some countries. Denmark, which dropped all pandemic restrictions in January, including masks, is now seeing record high case counts with the BA.2 sub-variant dominant.
A recent study, led by Japanese researchers, argues that BA.2 is different enough from BA.1, and a bigger threat to public health, that it should not be considered Omicron at all, but should be given its own Greek name.
The study found that it transmits at 1.4 times the rate of BA.1, replicates more easily in nasal cells and that experiments in hamsters show it is more virulent than BA.1
“Our multi-scale investigations suggest that the risk of BA.2 for global health is potentially higher than BA.1,” wrote the authors.
Early research on BA.2 suggests that people who have been infected with BA.1 will not be re-infected with it, said Otto, who is tracking the sub-variant. That could lessen its impact in Ontario where, according to Dr. Peter Juni, scientific director of Ontario’s Science Advisory Table, some 3.5 million people were infected with Omicron between the beginning of December and the end of January, giving them immunity to the new sub-variant.
Its virulence compared to the earlier sub-variant is not entirely understood, said Doug Manuel, a senior scientist at The Ottawa Hospital Research Institute and a member of Ontario’s Science Advisory Table, but he said there are no “red flags” suggesting it could be more virulent. Fully understanding its implications will take time, he said.
In a report released this week, the B.C. COVID-19 modelling group, of which Otto is a member, found that BA.2 represents about 35 per cent of all COVID-19 cases in Alberta, nearly 12 per cent of cases in Ontario and 8.3 per cent of cases in British Columbia. Otto cautions that data about genetic sequencing of SARS-CoV-2 is frequently delayed and fragmentary across the country, which could mean BA.2 is now more widespread and could represent as much as 99 per cent of cases in Alberta and 34 per cent of cases in Ontario.
Alberta, which dropped pandemic restrictions relatively quickly before the Omicron wave really began to diminish there, could see a bigger impact from the BA.2 variant, she said, such as a prolonged peak or double peak.
Ontario, where case counts have dropped steadily in the past month, could be “spared the worst” of the BA.2 wave, she said. That is largely because so many people were infected with the original sub-variant of Omicron and booster rates are high.
Juni, who supports the province’s stepped reopening plans, says BA.2 will represent less of a challenge to the province since its main difference over BA.1, so far, appears to be transmissibility.
Manuel said scientists, including wastewater researchers, continue to watch BA.2 closely.
He said he and others have been paying close attention to Denmark, which was one of the first countries to drop all pandemic restrictions. But, unlike Ontario, Manuel said Denmark opened up completely while cases were still increasing.
Ontario, which will drop most pandemic restrictions aside from indoor masks on March 1, is opening more cautiously than many jurisdictions at a time when the Omicron wave is receding. But many say masking requirements should not be lifted until the impact of reopening, and of the new sub-variant, are reviewed and understood.
Otto cautioned against dropping mask mandates too soon, saying mandating masks in public places such as buses and in grocery stores is a “mild inconvenience” that can have a substantial impact on reducing transmission when cases are still relatively high.
Premier Doug Ford suggested this week that he would like to see all pandemic restrictions gone sooner rather than later, saying he is “done with the pandemic.”
