Ontario COVID-19 modelling projects moderate rise in infections, hospitalizations after mask mandate lifts

Theglobeandmail.com
March 18, 2022
Dustin Cook and Carly Weeks

As COVID-19 measures are relaxed across the country, health experts in Canada’s most populous province are projecting another jump in cases, but not expecting a major hit to the health care system.

While officials are keeping an eye on the highly transmissible BA.2 Omicron subvariant, which has seen a surge in parts of Europe, new modelling released by Ontario’s COVID-19 Science Advisory Table on Thursday predicts a moderate rise in infections and hospitalizations over the next few weeks just as federal travel restrictions ease and the provincewide mask mandate comes to an end.

Wastewater data are starting to show a slight increase in cases across the province, estimating between 15,000 and 20,000 cases daily.

In its report, the advisory table did add a caveat to its modelling, saying the impact on hospitals and ICU admissions is difficult to predict and dependent on many variables, including the potential spread of BA.2.

Assistant scientific director Karen Born said although restrictions are being lifted, Ontario isn’t out of the woods yet and it is possible that masking and proof of vaccination will again be needed.

“Mandates are something that may need to come back into play, but all these decisions need to be data-driven and the global pandemic is not over,” she said in an interview. “We are at a moment now that the wave has declined, but I think the key message is to be prepared for future waves and to know that masking is still a very effective intervention.”

If Ontarians increase close contacts by 40 per cent, with half of them not wearing a mask, the group projects ICU cases could spike to about 300 in May. Overall hospitalizations are expected to rise, but not surpass 1,000 as they did during the most recent wave.

There are currently 644 COVID-19 patients in Ontario hospitals, including 199 in ICU, dipping under 200 for the first time this year.

The Quebec government said this week it doesn’t intend to bring back any of the already removed COVID-19 restrictions and Health Minister Christian Dube tabled a bill Wednesday to end the public-health state of emergency. The province, which endured some of the worst outbreaks in the country, lifted almost all remaining measures last week, but masking in public, indoor spaces is expected to remain until mid-April.

In Alberta, the proportion of lab-confirmed COVID-19 cases involving BA.2 has been increasing recently. The subvariant accounted for 33 per cent of cases from March 4 to March 10, according to a weekly update from Alberta Health Services posted to the agency’s website. The original BA.1 form of Omicron remains dominant, accounting for the rest of the cases during that time period.
Alberta’s Chief Medical Officer of Health Dr. Deena Hinshaw said the province is monitoring the spread of BA.2 and watching data emerging from other countries, which she said is a reminder that the COVID-19 pandemic is not over. She said it’s not clear yet how the subvariant could affect the health care system.

“It’s important to remember that what we’ve seen in other countries is that while BA.2 seems to transmit more effectively, it does not seem to be a higher risk for severe outcomes,” Dr. Hinshaw said earlier this week.

Omicron has several sublineages, including BA.1, which was the most commonly reported until recently. BA.2 is now making up a greater proportion of COVID-19 cases and, in some parts of Canada, quickly becoming the dominant sublineage.

Dr. Srinivas Murthy, who studies pandemic preparedness at the University of British Columbia, said it’s not at all surprising to see a more transmissible sublineage and that more will likely emerge as time goes on. But each time a new sublineage or another variant is detected, it’s important to determine how transmissible it is, the severity of illness it causes and the level of protection offered by pre-existing immunity from vaccines and prior infection.

“We will have these small -- hopefully small -- wavelets or surges or whatever we want to call them,” said Dr. Murthy, who is an associate professor in the faculty of medicine at UBC. “It’s just a matter of how evasive they are to our immunity.”

While people who are vaccinated may be more likely to be infected with Omicron sublineages, the risk of severe illness is much higher in people who are unvaccinated.

Dr. Murthy said while the pandemic isn’t over, access to vaccines, treatments and other protective measures has significantly improved the situation for many in Canada.

“We’re in a much better spot than we were a year and a half ago, two years ago,” he said.

Ontario’s Minister of Health Christine Elliott said earlier this week the province is closely monitoring the BA.2 surge in other countries and is expecting it will soon make up a significant number of new cases.

“We expect that it may be 50 per cent of the cases that we have in Ontario within the next short period of time,” Ms. Elliott told reporters on Tuesday, noting Ontario’s Chief Medical Officer of Health Kieran Moore feels the province can handle this variant without any further disruptions to the health care system.

Responding to the projections Thursday, Ontario’s Ministry of Health said hospital cases have been trending downward and the province has the capacity to provide care for patients if there is a spike.

“Ontario has done significantly better than the best-case scenario provided in the last modelling,” spokesperson Alexandra Hilkene said in a statement. “We have continued to maintain capacity to provide care for all patients who need it and our hospitals can manage any range in these latest projections.”