Data suggests that Canada is at the start of the Delta-drive fourth wave of COVID-19.
Federal public health officials, including chief public health officer Dr. Theresa Tam, presented updated COVID-19 modelling data at a press conference on July 30.
Based on longer-range forecasts, which show how the pandemic may evolve through early September, Canada has entered a fourth wave.
“The data suggests that we are at the start of the Delta-driven fourth wave,” Tam said.
“But the [pandemic’s] trajectory will depend on vaccinations, as well as the timing, pace, and extent of reopening.”
Tam noted that some increase in cases is expected as public health measures are eased across the country.
If Canadians maintain their current contact levels, cases will increase “modestly,” as illustrated by the grey line in the graph below. This scenario would lead to roughly 1,500 new COVID-19 cases being reported daily by September.
However, if people increase their daily contacts by 25%, Canada could see upwards of 10,000 new cases each day by summer’s end, an outcome represented by the blue line.
“This forecasts 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 vaccine coverage,” Tam said.
Based on international experience with the Delta variant, Canada must maintain precautions until full vaccination rates are higher.
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If vaccination rates increase among those aged 18 to 39, the impact of a “serious resurgence” in the fall or winter would be reduced.
“We expect cases to be concentrated largely in younger, unvaccinated people,” Tam said.
If the age group does not increase its vaccination rate, Canada’s hospital capacity could be exceeded by January 2022, due to the Delta variant.
As of July 24, 69% of 18 to 29-year-old are fully immunized, while 73% of those aged 30 to 39 are doubly vaccinated.
Nationally, data from July 29 shows that 81% of Canadians aged 12 and older have had one dose of a COVID-19 vaccine, while more than 66% are fully immunized.
Tam noted that officials are monitoring the need for a COVID-19 booster shot, although the priority remains first and second doses.
The Delta variant is the most transmissible variant detected to date – there has been a five-fold increase in Delta cases since June.
The variant leads to an increased risk of hospitalization, and reduces the effectiveness of symptomatic infection after one vaccine dose.
“Vaccination is proving to be highly effective against severe illness,” Tam said.
From December 14 to July 12, 84.9% of those hospitalized with COVID-19 were unvaccinated. More than 89% of all cases during that timeframe were detected in unvaccinated people.
“[The] modelling underscores that increasing first and second dose uptake in young adults can have a big impact on building up better protection in the fall and winter,” Tam said.
“The bottom line is: get vaccinated.”