Canada's COVID-19 models 'give us hope': If vaccines continue, public health restrictions could lift by summer, experts say

Elisabetta Bianchini
·4 min read
Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)

New Canadian modelling data, presented by Dr. Theresa Tam, Canada’s chief public health officer, and Dr. Howard Njoo, the deputy chief public health officer, shows that Canada could see public health restrictions safely loosened this summer.

Dynamic modelling examined the different scenarios for lifting public health restrictions based on interconnected factors, including vaccine effectiveness, vaccine rollout, and the impacts of variant of concern on epidemic growth and severe outcomes. The projection looks at hospitalization capacity and adjusting restrictive measures when 20 per cent of Canadians have received their second dose.

"These models give us hope, illustrating that there is a safe way to lift more restrictive public measures, like certain workplace and business closures by this summer if enough people get vaccinated," Dr. Tam said. "In the plausible safe lifting scenario...if enough people get vaccinated and assuming vaccine rollout proceeds as planned, by mid-summer at least 75 per cent of adults age 18 years and older will have received the first dose and 20 per cent will have received a second dose."

"At this point, restrictive measures could be gradually eased as long as adequate test, trace, isolate capacity and individual precautions are maintained."

The plausible alternate scenario assumes lower vaccine uptake, with only 55 per cent of eligible adults being vaccinated with their first dose and 20 per cent with their second dose by mid-summer, which will see overwhelmed healthcare capacity into the fall.

"It's the data on the epi-curve and the epidemiology that is going to drive a local jurisdiction to lift public health measures but you can't do it too quickly," Dr. Tam said. "We need as many people vaccinated as much as possible."

Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)
Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)

Looking at the impact of vaccinations on the COVID-19 situation in Canada, longer range forecasting predicts that if heavily impacted areas of the country had not strengthened public health measures, COVID-19 cases would have surged sharply.

"If implementation and adherence to measures is moderately effective, reducing contact rates between people by 30 per cent,...the epidemic is forecast to plateau at the current elevated level of activity, with hospitalizations and critical illnesses continuing to place a heavy strain across the healthcare system," Dr. Tam explained. 

"However, if measures are strongly effective, reducing in-person contact rates across the community by 40 per cent, as we observed in January, the epidemic is forecast to come under control... The early effects of vaccination will help us achieve this reduction."

Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)
Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)

Surveillance data from Mar. 25 to to the beginning of April were plotting along a "strong resurgence trajectory," Dr. Tam highlighted, predicting that public health measures were not stringent enough to combat the rapidly spreading variants of concern in Canada.

"Since about mid-April, as restrictions in high-incidence areas began to take effect, surveillance data points...are pointing below the strong resurgence trajectory, indicating that these measures are starting to slow the spread," Canada's chief public health officer said.

Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)
Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)

Short-term forecasting shows that Canada could see between 1,209,780 and 1,281,040 cumulative COVID-19 cases by May 2, and between 24,000 and 24,570 cumulative deaths.

Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)
Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)

Canada's case counts are now more than double what they were a month ago, with an average of 8,444 cases reported daily over the past week. The average number of people in hospitals and ICUs has doubled or more since late March.

Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)
Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)

Variant of concern make up more than half of recent COVID-19 cases in Canada, with the B.1.1.7 variant accounting for over 95 per cent of the variant cases to date.

Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)
Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)

On a more positive note, Canada's effective reproductive number, how many people are being infected by each new case, is now below one after trending above that threshold since early March.

"This means that for the first time in many weeks, the epidemic has dropped out of a growth pattern, primarily driven by recent declines in epidemic growth in Ontario, Quebec and British Columbia," Dr. Tam said.

Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)
Update on COVID-19 in Canada: Epidemiology and Modelling (Public Health Agency of Canada)

About 30 per cent of Canadian adults have received at least one dose of a COVID-19 vaccine, increasing to more 68 per cent of adults in the Territories.

Over 86 per cent of adults age 80 or older have received at least one of COVID-19 vaccine, contributing to a reduced rate of infection in this age group.