While COVID-19 vaccines continue to be administered across Canada, the latest national modelling data shows that there are signs of epidemic growth in some areas of the country.
The seven-day moving average for Canada's reproductive number (Rt) has been trending above one since June 18, after several weeks of "trending out of an epidemic growth pattern with values below one," Dr. Theresa Tam, Canada’s chief public health officer, identified on Friday, while adding that lower case counts overall can lead to more fluctuations in Canada's Rt value.
"While most jurisdictions, remain out of the epidemic growth pattern, some are showing signs of increased disease activity and Rt trending above one, as restrictions have been eased," she said. "This growth is not unexpected, but it will be important to respond to new cases and clusters through testing, case finding and targeted vaccination efforts to slow the spread."
"If Rt remains persistently above one for several weeks, with predominance of the highly contagious Delta variant, we could expect to see a return to rapid epidemic growth, particularly as measures that slow the spread are eased."
To date, over 81 per cent of the eligible population has received at least one dose of a COVID-19 vaccine, with over 66 per cent fully vaccinated.
Data from the provinces and territories for mid-December to July 12 found that 0.5 per cent of cases were in fully vaccinated people, infected 14 or more days after the second dose. Only 0.7 per cent of hospitalized cases occurring in fully vaccinated patients.
The majority of cases, hospitalizations and fatal outcomes are occurring among unvaccinated people in Canada.
Short-term forecasting predicts an increased rate of growth for cumulative cases but not for cumulative deaths. It has been predicted that Canada will see between 1,432,555 and 1,441,610 cumulative COVID-19 cases by Aug. 8, and between 26,570 and 26,700 deaths by the same day.
The longer term forecasting looks to September, predicting a "stronger resurgence if community-wide contact rates increase too quickly, highlighting the need for ongoing caution."
"It suggests we are at the start of the Delta driven fourth wave, but that the trajectory will depend on ongoing increase in fully vaccinated coverage and the timing, pace and extent of reopening," Dr. Tam said.
"We expect cases to be concentrated largely in younger unvaccinated people, with further spread extending into older, unvaccinated populations. Both higher case volumes and older age of cases could ultimately increase severe illness and hospitalization rates."
The modelling shows that if Canadians increase the number of people they come in contact with each day by 25 per cent, reported new cases with exceed 10,000 daily. If we maintain the current level of community contacts, Canada will see a "modest increase in cases," with under 2,000 reported cases each day.
"This forecast reaffirms the need to take a cautious approach to relaxing public health measures, to remain vigilant and responsive to signs of resurgence, and to continue to increase first and second dose vaccination coverage," Dr. Tam said.
Federal health officials also stressed that increasing vaccine uptake in young adults between the ages of 18 and 39 could reduce the impact of a fall and winter COVID-19 resurgence.
"Even with 72 per cent vaccine acceptance in 18 to 39 years olds there is still a risk that healthcare capacity could be exceeded with a Delta driven wave, even when taking into account very high coverage in older age groups," Dr. Tam said.
"The good news is that there are still opportunities to reduce this risk. If the proportion of fully vaccinated 18 to 39 year olds were to increase to 80 per cent, this could significantly reduce the size and impact of the resurgence."