Random testing at Canada’s border cannot distinguish between people who previously had COVID-19 and those who are currently infected with it, according to a government statement obtained by Global News.
The mandatory measure, which affects about 1 in 20 fully vaccinated people entering Canada by air, is also causing healthy travelers to be forced into quarantine.
The tests that are used (PCR or molecular tests) are too sensitive to distinguish between active infections and past infections.
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Still, the government insists on using these tests because it says they are the “gold standard” for detecting the virus, even if they may be catching people who have fully recovered.
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“You’re shooting at a dartboard with a blindfold on,” said Colin Furness, an infectious disease specialist and epidemiologist at the University of Toronto.
“I want us to do disease surveillance. I want us to control transmission … but I don’t think your current plan is really effective at any of those things.
2:13 Mandatory random COVID testing of international travelers entering Canada to resume Mandatory random COVID testing of international travelers entering Canada to resume – July 19, 2022
Mandatory random testing of fully vaccinated travelers began in late 2021 to help control the spread of new variants entering Canada and to ensure that infected travelers are quarantined.
Approximately 5,000 people are selected each day, according to the government. The tests are carried out by a handful of private companies that have received hundreds of millions of dollars in government contracts since the start of the pandemic.
Random testing was widely criticized this spring as the source of unprecedented disruptions at Canadian airports. Critics said it was causing bottlenecks at customs checkpoints, which created cascading problems that led to flight delays and cancellations.
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The government halted testing at airports in mid-June to ease some of those pressures. But in the interest of continuing to track new variants, the program was restarted a month later, with tests self-administered at home or conducted at locations outside airports.
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Denise Chenier, who lives in San Francisco and recently traveled to Canada with her husband, Grant, was among those selected to test at Toronto’s Pearson Airport after the program was restarted.
The couple were flying to Thunder Bay to set up Grant’s mother’s estate and to celebrate her life.
The Cheniers arrived in Thunder Bay on a Saturday in late July, the same week that random testing resumed. Denise completed her PCR test the following Monday, which is when she said the government-contracted lab opened. He said it took several more days without the results.
When she contacted public health officials about the results, she said she was shocked to find out she tested positive and had to self-isolate for 10 days.
“I read it and thought, ‘That’s a typo,'” Denise said.
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The couple had recently recovered from COVID-19 and had both tested negative for multiple rapid antigen tests taken during a 12-day isolation period before their trip.
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They said it was unlikely they were reinfected with the virus before traveling because they limited contact with others, wore masks at all times and had two booster shots each.
They also said they did rapid antigen tests after arriving in Thunder Bay and the results were negative.
The couple said they explained their situation to local, provincial and federal health officials by phone, all of whom agreed the test likely picked up Denise’s previous infection.
But rules are rules, Denise said she was told, meaning she still had to quarantine.
“This was a huge imposition,” Grant said. “A waste of time and money.”
The government said all fully vaccinated travelers entering Canada have an “equal chance” of being selected for random testing. It doesn’t matter what country a traveler comes from, how long they’ve been away, or whether they’ve been screened for testing before.
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The government said its daily target of roughly 5,000 tests was set to ensure it has a “representative, reliable and robust estimate” of the number of people who are positive for COVID-19 at the time they believe the border
But the government also said its tests can detect past infections up to 180 days, meaning many of the positive test results could be old infections, as opposed to active infections.
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To avoid potential problems, including forcing people with previous infections to self-isolate unnecessarily, anyone who provides a positive PCR test result taken up to 180 days before entering Canada is exempt from the random testing program.
But access to PCR testing has been limited in many places over the past year, meaning travelers with previous infections are unlikely to be able to provide the test they need to get an exemption.
2:04 COVID-19: Quebec reserves PCR tests for high-risk groups COVID-19: Quebec reserves PCR tests for high-risk groups – January 5, 2022
The Cheniers, for example, were told by their family doctor not to bother with a PCR test because they had many symptoms of COVID-19 and because they tested positive on rapid antigen tests.
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The couple said they support testing at the border, but believe the random testing exemption should be extended to anyone who has previously tested positive on a rapid antigen test.
Meanwhile, in Ontario, access to PCR testing was restricted to “high-risk” people in December 2021. Anyone who was not considered high-risk and had symptoms of COVID-19 was he said to “assume” he had the virus without contracting it. a PCR test. The provincial government also expanded access to rapid antigen tests through workplaces and pharmacies.
James Hay, a postdoctoral researcher at Harvard’s Center for Communicable Disease Dynamics, said it is “highly unlikely” that someone will test positive for COVID-19 six months after infection.
He said research has shown that most people will begin to show negative results on a PCR test 10 to 14 days after infection.
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Hay also said rapid antigen tests, which are less sensitive than PCR tests, would be a more effective tool for detecting active cases of COVID-19 at the border.
“An antigen test is really very specific for that potentially infectious period because you have to have a lot of virus to get a positive antigen test,” he said.
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One useful method of doing this would be to give travelers two or three rapid antigen tests and ask them to complete the tests over several days, Hay said.
Anyone who tests negative repeatedly is unlikely to be infected with the virus, Hay said. Those who test positive are likely in the midst of an active infection and can be followed up.
“There’s still a role for testing, it’s where it’s done and how often it’s done that’s probably changing,” Hay said.
One of the main advantages of using PCR testing is that it allows for “sequencing” of the virus, which is needed to distinguish between different variants, Hay said.
This allows the government to monitor the spread of emerging variants, such as Delta and Omicron, and potentially prevent any serious threat to Canada by imposing new public health measures.
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That could include restricting flights from countries where data shows more contagious and potentially deadly variants are spreading or imposing stricter quarantine measures for international travelers.
“It could be an early warning sign,” said Caroline Colijn, a professor of mathematics at Simon Fraser University and an expert on the evolution of infectious diseases.
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Colijn, who sat on the federal government’s COVID-19 expert advisory panel, said it was important to understand the goals of any testing regime…