TORONTO — COVID-19 hospitalizations and ICU admissions will likely rise as more public health measures are lifted, but nowhere near the levels seen at the peak of the Omicron wave, Ontario's expert science advisers said Thursday.

New modelling released by Ontario's science advisory table — ahead of mask mandates being lifted Monday in most settings — suggests that if there is a moderate increase in COVID-19 transmission, hospitalizations will likely rise, though they won't exceed 1,000.

Transmission could moderately increase if people increase their contacts by 40 per cent and half of those contacts are not wearing masks, or if people increase their contacts by 30 per cent and half are maskless, but the more transmissible Omicron subvariant BA.2 becomes dominant.

Chief Medical Officer of Health Dr. Kieran Moore has said he expects BA.2 to become dominant this month.

There are currently 644 people in hospital with COVID-19, and a modelling graph suggests that there could be fewer than 900 hospitalization at a peak in early May — a far cry from the more than 4,000 people in hospital with COVID-19 in January.

"COVID-19 transmission, which drives hospital occupancy, can be reduced by wearing high-quality masks, full vaccination and not increasing contacts," the science advisers wrote.

The government should be prepared to reintroduce mask mandates, reintroduce vaccine certificates and require a third dose if necessary, and continue to improve ventilation and air filtration in public spaces, the experts said.

ICU occupancy may rise to about 300 in the moderate transmission increase scenario, the modelling suggests. In January it rose to nearly 600 people and in the spring of 2021 it was over 800.

Cases, hospitalizations and ICU admissions have steadily declined since that January peak, but the modelling shows that decline has stopped and is now plateauing across most of the province. Wastewater testing suggests cases are starting to increase slightly.

A true count of daily new COVID-19 cases is difficult to establish since the province restricted access to PCR testing. There were 2,398 new infections reported Thursday as confirmed through PCR, but Moore has said the actual daily number is likely 10 times higher.

It's likely that there are currently between 15,000 and 20,000 new COVID-19 cases each day, the science table wrote Thursday, and that between 3.5 million and four million people have been infected since Dec. 1.

A spokeswoman for Health Minister Christine Elliott said hospitals can continue to manage the case levels that are projected in Thursday's modelling.

“Ontario has done significantly better than the best case scenario provided in the last modelling and we now have the lowest rate of hospitalizations out of all provinces," Alexandra Hilkene said in a statement.

The science table also says that administration of COVID-19 booster doses has plateaued, but notes that the third doses helped cut hospitalizations and ICU occupancy by about 30 per cent at the peak of Omicron.

To best protect themselves against COVID-19, the science advisers recommend full vaccination — three doses for most adults and four doses for certain high-risk people — as well as wearing high-quality masks, and staying home when sick.

This report by The Canadian Press was first published March 17, 2022.

The Canadian Press