OTTAWA — Some 8,000 Manitobans will be invited to prick their finger and help scientists study the spread of COVID-19 in Canada, with a renewed survey seeking to learn how many people got infected without knowing it.
"It’s looking at levels of immunity of the population, and the potential long tail of this pandemic," said Dr. Catherine Hankins, a McGill University public health professor.
"We all want to figure out when is this going to end, when can we get out of it, and how we can open up and be safe."
Hankins co-chairs the national COVID-19 immunity task force, which uses a range of studies to track how many Canadians have been infected, how different vaccine combinations respond, and how immunity compares between vaccinated people who recovered from an infection compared with those who haven’t been exposed to the novel coronavirus.
That work is being expanded to look at Canadians with so-called long COVID, which means symptoms that linger from an infection that occurred more than three months prior.
"This is going to be very important for planning appropriate health services for some people," said the Montreal-based Hankins.
Previously, her team convinced slightly more than 10,000 Canadians to administer finger-prick tests between November 2020 and April 2021. A mere 2.6 per cent of participants had antibodies from a COVID-19 infection ahead of the third wave.
Working with the National Microbiology Lab in Winnipeg, her group had mailed out 48,000 testing kits to a sample of people Statistics Canada selected, who equally represent different regions, genders and ages.
The test involved using a provided pinprick and setting five blood drops onto a special paper card. Hankins said only 35 per cent of those selected filled out an online questionnaire and 23 per cent provided the dried-blood specimen.
Statistics Canada is now supplying kits to a sample of 100,000 Canadians, anticipating 45 per cent will fill out the survey and 35 per cent will provide the blood sample.
This time, Hankins’ team is sending out an explanatory letter a week before the test kit arrives, in the hope it will ease any worries about an unexpected package that demands a biological sample.
In Manitoba, 2,538 people will get test kits this week, followed by 2,739 each in the months of May and June.
The new questionnaire will ask questions such as whether the person believes they caught COVID-19, which vaccines they’ve received, what difficulties they’ve had accessing medical treatments or tests, and what lingering symptoms long-haulers have.
A blood and saliva sample will be tested to see what types of antibodies the person has — the test differentiates between those from vaccines and the ones from a previous infection. Some might have the latter without having ever tested positive for COVID-19.
"It might give us an idea of how many people are PCR-positive but asymptomatic," Hankins said. "It also tells us what proportion of people, and how far out from their infection or last vaccine dose, don’t have any antibodies."
The data could suggest how well people retain immunity over time, and whether that differs by age, gender and region.
The previous dried-blood survey found evidence of disproportionate COVID-19 infections among racialized groups, Canadians under the age of 19, and those with lower incomes.
"This is more representative and gives you more granularity," Hankins said of the new survey.
The task force has separately been doing recurring surveys of samples from blood donations, which have shown an uptick in antibodies as the Omicron variant took hold.
Given the decline in PCR testing, Hankins said blood surveys — from mailed-out tests and from blood bank sampling — can be used alongside wastewater surveillance and tracking health-care worker absenteeism, to get a sense of when COVID-19 is on the rise.
"We’re looking for different ways of seeing what’s happening, from different angles," she said.
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