Omicron BA.2 subvariant becoming dominant, representing potential risk
The rise of the more-contagious Omicron subvariant in Canada could represent a threat to the elderly and others who are vulnerable, warns a leading expert on BA.2.
The concern comes as Ontario and other provinces are dropping pandemic restrictions and immunity from third doses of COVID-19 vaccine is waning for many of the most vulnerable. Ontario is offering fourth doses to long-term care and other vulnerable residents.
The BA.2 subvariant, which is behind record case counts and deaths in some parts of the world, is on its way to becoming dominant in Ontario and across Canada. As of this week, about 50 per cent of new COVID-19 cases in the country are BA.2, squeezing out the original Omicron subvariant, BA.1, said Sarah Otto, a professor of evolutionary virology and mathematical modelling at the University of British Columbia. While cases of BA.1 are dropping across Canada, BA.2 cases are increasing slightly or remaining steady.
“We are moving from a BA.1 wave to a BA.2 wave,” Otto said.
Canada should fare better than many countries from BA.2 because there is so much immunity from vaccines and Omicron infections, she said. Instead of a steep spike in new infections, as happened when Omicron arrived in December, Otto expects to see something more like a bump. Canada is fortunate BA.2 is arriving here relatively late after BA.1. People who were infected with BA.1 are unlikely to become infected with BA.2, she said.
While she doesn’t expect case counts to be as high as in the original Omicron wave, the arrival of BA.2 does represent a threat to those who are vulnerable and might have waning immunity, she said, and are more likely to get seriously sick if infected.
Research shows that, three months after receiving a booster dose, the chance of becoming hospitalized with an infection roughly doubles.
“That is what I am concerned about,” Otto said.
The timing of BA.2 coincides with what is likely waning immunity from vaccines for long-term care and other residents, who were among the first to receive booster doses.
While thousands of eligible Ontarians have now received fourth doses of vaccine, thousands more likely have waning immunity. In Ontario, more than 115,000 people have received fourth doses, according to the health ministry. In Ottawa, just over 10,000 people have received fourth doses.
There is also a sizeable percentage of the population that is still susceptible to Omicron infection as the highly contagious BA.2 becomes more widespread.
The rise of BA.2 also coincides with the dropping of pandemic restrictions. Provincial vaccine mandates were dropped this week. Many institutions, including hospitals and long-term care homes, say they plan to leave vaccination mandates in place.
Next week, when Ontario students return from March break, there will be no mask mandates in schools. The organization representing pediatric hospitals and health organizations has asked the province to keep mask mandates in place in schools for at least two weeks after the break to prevent a resurgence of cases in schools and the community. Others are calling for masks to remain in place until the end of the school year.
In a letter to Premier Doug Ford, a group of health leaders and experts says masks are critical tools to keep long-term care residents safe, as are mandatory vaccinations and continued rapid testing.
The group also called on the province to actively encourage vaccination and boosters for seniors, essential caregivers and staff in long-term care, noting that evidence is emerging that vaccine effectiveness against infection decreases over time.
Long-term care chains and other large homes, as well as long-term care homes run by the City of Ottawa, will continue to require vaccines and masks, but doing so is more difficult for smaller homes that don’t have the same legal resources, says the organization representing not-for-profit and municipal homes in the province.
“It is just such a vulnerable population, why wouldn’t you continue (the mandates)?” asked Grace Welch, co-chair of the Champlain Region Family Council Network.
Dr. Benoît Robert, chief medical officer at Perley Health and head of the association representing long-term care clinicians in Ontario, said vaccines and masks represented freedom for long-term care residents who had been isolated and had their lives disrupted during the last few years. Perley will continue to require vaccines for staff and masking for staff and visitors. It will also screen visitors.
“At this time, it is wise to continue with masking inside the long-term care home.”
Long-term care outbreaks spiked during the Omicron wave and have since dropped, but there are still outbreaks, including at a handful of Ottawa long-term care homes.
Given what is on the horizon with BA.2, Otto said she would like to see masking continue across the country.
“It is one thing we are doing that really helps reduce transmission.”
What we know about BA.2
1. It is different from BA.1, the original Omicron subvariant, in its genetic sequence, but it doesn’t appear to be able to evade immunity from BA.1. That means people who were infected with BA.1 are unlikely to be infected with BA.2. Up to one out of every fourth person in Ontario is estimated to have been infected with BA.1.
2. It spreads more easily than BA.1. Studies are ongoing to understand why.
3. It doesn’t appear to cause more severe disease than BA.1. Its more rapid spread, though, could result in high rates of hospitalization in places with low immunity from vaccines or prior infection.
4. Canada is in a fairly good spot when it comes to BA.2, according to Sarah Otto, a professor of evolutionary virology and mathematical modelling at the University of British Columbia, because it arrived after an intense BA.1 wave which built up immunity in addition to high vaccination rates.
5. About a dozen nations around the world are now seeing spikes in infections driven by BA.2. In places that had so-called Zero COVID policies, outbreaks are severe and rapid.