As the U.S. reopens its land border, some experts say the Canadian government should consider scrapping its costly COVID-19 PCR test requirement for fully vaccinated travellers — particularly for short cross-border trips.
Instead, they suggest Ottawa could look at using the less expensive, faster and more convenient antigen tests, which are used to screen travellers in the U.S., but are also less reliable.
“Wouldn’t it make more sense to have [an antigen test] done at the border rapidly? You can get one done in 15 minutes or even faster … rather than a 72 hour-old [PCR] test that’s sometimes logistically difficult [and] expensive to get,” said Amesh Adalja, an infectious disease physician and a senior scholar at the Johns Hopkins Center for Health Security in Baltimore.
“From the scientific standpoint, the antigen tests make more sense,” he said, pointing to the fact antigen tests are done much closer to the time of the crossing. “So I think that the U.S. policy is actually a better one.”
Currently, recreational travellers entering Canada must show proof of a negative molecular test — such as a PCR test —taken within 72 hours of their departing flight or planned arrival at the border. But those tests can be expensive, running up to $300, and can take up to 24 hours — or longer — for travellers to get their results.
It’s particularly prohibitive for families, as the molecular tests are required for everyone over the age of five. That means for a family of four, it can add $1,000 to the cost of a trip.
Molecular tests more sensitive
Some countries, like the U.S., only require a rapid antigen test, which costs as little as $20 and provides results in as little as 15 minutes.
But antigen tests aren’t as sensitive as molecular PCR tests (or polymerase chain reaction tests), meaning antigen tests can miss low levels of the virus.
“It leads to a high false-negative because your body has to generate enough of the virus for it to show us a positive result,” said Warren Chan, a professor of biomedical engineering at the University of Toronto
“In a PCR test, the level at which you can detect is significantly much lower. So if you’ve been infected with a [low level] of the virus, PCR tests would be able to pick it up, but antigen tests cannot.”
Dr. Fatima Kakkar, a Montreal-based pediatric infectious disease specialist, agreed that the PCR test is the “gold standard” of testing for COVID-19.
If PCR tests are a 100, she said, an antigen test would be about an 80 or 90, meaning that they could be missing up to 20 per cent of people with COVID-19.
‘Reasonable to ask the question’
That means it was certainly reasonable for Canada to require the PCR test before vaccines became widespread, said Kakkar.
“Now that we’re all vaccinated, the question is: Is it OK to take that risk?,” she said of the calls to switch to antigen testing. “And I think it’s reasonable to ask the question right now.”
Canadian and American politicians representing border communities will hold a news conference Monday to call on the federal government to lift the PCR testing requirement.
On Friday, Chief Public Health Officer Theresa Tam acknowledged that the PCR testing policy was being “actively looked at.”
Dr. Zain Chagla, an infectious diseases physician at St. Joseph’s Healthcare in Hamilton, said he too believes the antigen test should be considered.
“If we’re trying to prevent people from entering Canada with active COVID-19, doing an antigen test at the airport is probably even more accurate than a 72-hour-ago PCR test, because you’re catching people that are infectious at that moment as they enter Canada.”
According to microbiologist and infectious disease physician Dr. Marek Smieja, as long as masks are worn in addition to vaccination, and ill passengers are prevented from travelling, there should probably be only a limited role for testing.
“For fully vaccinated, either no testing at all or antigen testing before travel would be appropriate. PCR testing is expensive and obtaining testing has been unnecessarily complicated,” he said in an email to CBC News.
“It either needs to be simpler or cheaper, or eliminated altogether.”
Testing upon return to Canada should ideally continue, he said, but that should happen through self-collected PCR tests — and those tests should be free of charge. The objective would be to help monitor which strains of COVID-19 are coming into the country, said Smieja, who is also the scientific director of McMaster HealthLabs in Hamilton.
The calls to rethink Canada’s PCR policy for those returning to the country have been particularly loud when it comes to short trips across the U.S. land border — which reopened Monday — with questions raised as to what protections those tests will actually provide.
“I’m not sure I understand the rationale for testing travellers who are going to the U.S. for a very short trip,” Dr. Irfan Dhalla, co-chair of a federal advisory panel on COVID-19 testing and screening, told The Canadian Press.
“Even if we were going to require tests from these travellers, a test taken in Canada, before the trip even starts, would not be helpful.”
Kakkar agreed that the government might have to re-examine their testing policies regarding short trips because they don’t “make much logical sense.”
The 72-hour policy was designed for people going on vacation or who would be out of the country for an extended period of time, and might potentially get infected while abroad, said Dr. Christopher Labos, a Montreal-based cardiologist with a degree in epidemiology.
“It doesn’t have the same utility for somebody who’s day-tripping, who’s crossing the border and coming back either for travel or for work, because of the time it takes for you to become symptomatic and to test positive for the virus,” he said.
“If you day-trip to the U.S. and come back, getting tested in the U.S. is not going to pick up any infection that you acquired that same day,” he said. “I think that’s an obvious place where that testing strategy isn’t all that helpful.”