More transmissible Omicron subvariant rising as Alberta mulls lifting more restrictions

A more transmissible Omicron subvariant is slowly picking up steam in Alberta, but experts say it's unclear how that could impact community transmission of COVID-19 at a time when the province is on the downward slope of the fifth wave.

Alberta resumed screening all positive COVID-19 cases for variants of concern on Wednesday after cutting back over Christmas when cases spiked.

According to the provincial lab, between eight and 15 per cent of daily COVID-19 cases — identified through PCR testing in the past week — have come back positive for BA.2.

"BA.2, based on this latest data, is not predominant, but still it's a rising trend over time," said Sarah Otto, a University of British Columbia professor and member of an independent B.C. COVID-19 modelling group.

Alberta's provincial lab is reporting a rolling seven-day average BA.2 positivity rate of 10 per cent, up from four per cent on Feb. 9, when the lab adopted a rapid screening test for the subvariant.

These numbers are based on PCR tests, which many Albertans have been unable to access since the province restricted testing to high priority groups — including health-care workers, people who work in high-risk settings such as correctional facilities, and some people who are considered high risk for severe illness.

Unvaccinated at risk

Dr. Lynora Saxinger, a University of Alberta infectious disease specialist, said it's difficult to know exactly how this subvariant — which does not appear to cause more severe illness than the original Omicron variant — will play out.

"It seems to be able to outcompete Omicron BA.1, which means that it likely would become the dominant strain over time. But the vaccine protectiveness is about the same. So what we would tend to see is more aggressive spread in an unvaccinated population possibly and more or less similar spread in the vaccinated population," she said.

"The Omicron subvariant especially seems to be so incredibly transmissible that I am concerned that it will be able to seek and infect people that are susceptible and that we'll have a really long plateau, where people are still going to be getting sick."

According to Saxinger, the most susceptible people are the unvaccinated and those who don't have three doses.

She said U.K. data over the last four months shows people with only two doses of the COVID-19 vaccine are four to seven times more likely to be hospitalized than those with three doses.

As of Thursday, 35 per cent of Albertans had received a third shot.

"It certainly is possible that we could see a plateau. It's possible we could see a surge, especially among unvaccinated people. It's also possible that it could just continue to slowly drop over time," Saxinger said.

"If we are going to be on a path of reducing public health protections, then we really have to pair that with a really serious push to get people to get their third dose and to get people who have not been vaccinated to get vaccinated because that's going to make all the difference."

Meanwhile, Otto said the BA.2 trends in Alberta are comparable with those in B.C. And she's pleased the province is screening for subvariants.

But with limited PCR testing and without solid case numbers in Alberta, she said, its hard to predict what will happen next.

The Kenney government's plan to further lift public health measures adds another layer of uncertainty to the mix, she said. The province is expected to announce on Saturday its final decision on moving to Stage 2 of its three-step plan to lift restrictions.

"My hope is that BA.2 is at low enough frequency in Canadian provinces that the immunity built by BA.1 and by people getting boosters is going to prevent a BA.2 wave from happening."