With 10,000 pinpricks, Prabhat Jha hopes to discover what no one else can see: How many Canadians have been affected by COVID-19?
Dr. Jha, director of the Center for Global Health Research at St. Hospital. Michael in Toronto, led one of the first large-scale surveys in the country that will examine participants’ blood for specific antibodies to the virus that causes COVID. -19.
Antibodies are a natural part of the body’s immune response. Initial studies with COVID-19 patients showed they appeared about three weeks after infection occurred and lasted for at least 60 days.
Because the first wave of infections in Canada is expected to peak in mid-April, Dr. Jha said now is the ideal time to try to get a picture of how widespread this disease has spread to the entire population. Starting this week, he and his team will start sending kits that participants can use to provide blood samples for the survey.
“The faster we release it, the more likely we will catch the peak of the antibody response,” Dr. Jha, who is also a faculty member at Toronto’s Dalla Lana University School of Public Health.
Unlike tests used to determine whether a person has an active case of COVID-19, antibody or serological tests can reveal who has previously found the virus. Even those without symptoms are expected to have antibodies if exposed.
Because so many cases of COVID-19 are not expected to be reported, a large survey using an antibody test is seen as the only way to measure the true level of a pandemic in Canada.
The challenge with such efforts lies in the collection of representative population samples to ensure meaningful results.
As a comparative example, a study of more than 3,300 adults conducted in early April in Santa Clara, California, estimated that more than 50 times more people in the community were exposed to COVID-19 than were known from confirmed cases at the time. But because subjects were recruited through Facebook, critics said the results tended to be skewed by participants who had reasons to suspect they had been infected and were motivated to find out.
This study also uses commercial tests that are prone to produce false positive results when antibodies to corona viruses are found in addition to COVID-19.
To avoid similar problems, Dr. Jha said he and his colleagues worked with polling company Angus Reid to collect research samples of 10,000 Canadians between 18 and 85 who would be invited individually to participate. Participants will be selected from a larger group that has been previously identified by the survey agency for various surveys.
Short door-to-door, “our sample is purely a random sample,” said Ed Morawski, president and chief operating officer of the company.
To help reveal how much the disease affects older Canadians, at least 4,000 of those sampled were 60 or more.
Each participant will fill out an online questionnaire and then, if he agrees to continue the survey, will receive a sample device with a finger prick and a container that can be closed to send back five patches of dried blood on a paper card, Dr. Jha said. This approach has been widely used in global health studies because it does not require participants to travel to the clinic to have their blood drawn.
Dr Jha said the team was still reviewing which antibody tests would be used after samples began to enter, but added that the project could use a large-scale testing platform designed for research rather than diagnostic.
“We will probably use two [tests] at least, in combination, “he said, adding that the results would be cross-examined to increase confidence. Participants will then learn whether it is very possible, somewhat possible or impossible that they have COVID-19.
Jha reminded that the positive results from the survey should not be considered a “passport of immunity,” based on limited information currently available about disease characteristics and the relationship between antibodies and immunity.
However, participants will also be asked to give a second sample in four to six months to see how long antibodies remain in the blood and to help determine COVID-19 immune levels in Canada.
Timothy Evans, director of McGill University’s global population and health school and member of the federal government’s immune task force, said St. Michael’s efforts were one of several that had been proposed to fill important knowledge gaps about the state of the pandemic in Canada over the next one to two months .
Another, organized by the British Columbia Disease Control Center, is still in the planning stages, said Mel Krajden, medical director of the center’s public health laboratory.
“B.C. has a very low prevalence [of COVID-19] only based on clinical cases, so this belongs to a different category, “he said.
Dr. Krajden added that a survey of 10,000 people might not be enough to accurately depict the effects of COVID-19 which varied greatly across Canada, especially in under-represented populations, such as indigenous peoples.
Jha said that with sufficient funds, he would also prefer to increase the amount. “I want to do 100,000 Canadians – the more the better,” he said. “We will work hard to get the best portrait of the country we can.”
Our Morning Renewal and Night Renewal Bulletins are written by the editors of the Globe, giving you a brief summary of today’s headlines. Register today.