Testing all incoming air travellers for COVID-19 is of low value with the disease now widely circulating in the community, and Canada’s limited PCR testing resources should instead be used on random sampling to identify variants, say medical experts calling for and supporting a shift in strategy.
Among those recommending a change is Canada’s Chief Public Health Officer, Theresa Tam, who signalled that an announcement on measures at the border would come this week.
“We do have to adapt our border stance because we know it’s pretty impossible to reduce every single case of importation; it’s already in Canada and it’s transmitted widely throughout our communities,” Dr. Tam said at a news conference on Friday.
“But we still do have to look out for other variants, and new variants, and try to detect them as early as possible and reduce their potential impacts to at least slow them down so that we can understand them better.”
The expected change comes as some provincial governments begin lifting local COVID-19 restrictions, and the transportation and tourism sectors prepare for the third spring break of the pandemic. In January, the chief medical officers with Air Canada, WestJet and Toronto Pearson International Airport penned an open letter to Ontario and federal health officials noting that their organizations have achieved a positivity rate that is a fraction of that in the community, and that PCR tests would be better used in long-term care, hospitals and schools rather than at airports.
Between Nov. 28 and Jan. 22, 5 per cent of 719,678 vaccinated air travellers, and 6.5 per cent of 145,357 partly or unvaccinated air travellers, tested positive for COVID-19 as they were entering Canada, according to federal data. This peaked during the Omicron-driven wave in early January, with about 8.5 per cent positive and 10.8 per cent positive for vaccinated, and partly or unvaccinated air travellers, respectively.
In comparison, the average daily positivity rate across Canada, from the past seven days, is 15.8 per cent positive.
Meanwhile, 0.8 per cent of infections were contracted during international travel, and 0.5 per cent from contact with a traveller, according to millions of case reports submitted to the Public Health Agency of Canada by provinces and territories.
(People are required to be COVID-19 vaccinated to board planes and trains, something that Prime Minister Justin Trudeau said will not be changing any time soon.)
Zain Chagla, an infectious diseases physician and associate professor at McMaster University, is among those calling for an end to PCR testing for air travellers.
At a news conference on Friday, Dr. Chagla noted that many people who recently contracted COVID-19 during the Omicron surge were unable to access testing and therefore could not receive confirmation of a previous positive. Meanwhile, studies have shown people who have recovered can continue to test positive on PCR tests for several months, despite no longer being infectious.
This could mean that a traveller tests positive from a prior infection and is stuck in a foreign location left to deal with travel delays and financial penalties with no meaningful benefit, Dr. Chagla said.
“It’s going to lead to a lot of disruptions of travellers that, again, did the right thing and essentially could not get tested and have a molecular test document it before they return,” he said.
Currently, all travellers aged 5 and up returning to Canada by air must provide a negative molecular test, such as a PCR test, taken within 72 hours of their scheduled flights, or a positive test result taken between 10 and 180 days before entering the country. (The quicker, cheaper rapid antigen tests are not permitted.) Upon landing, some may be selected for randomized arrival testing.
In January, Dr. Tam noted that tracking every case was both unnecessary for surveillance and a “capacity drain on the system as a whole.”
“What is really important for the border is a really good random sample, where you are not just following Omicron, but following the other variants,” she said.
In the fall of 2020, researchers from the University of Toronto and McMaster University conducted a study involving more than 16,000 international passengers at Toronto Pearson International Airport to determine whether a 14-day quarantine period was necessary. (They concluded that 94 per cent of those who tested positive were identified by Day 7, and that a reduced quarantine period combined with testing can be as effective as a 14-day quarantine.)
Vivek Goel, the study’s lead author and now president of the University of Waterloo, noted that the study was conducted before vaccines and variants of concern, and said that developments since then have changed the utility of COVID-19 testing for air travel.
“If we continue to maintain requirements for all travellers to be vaccinated, the value of universal screening or testing is very limited,” he said.
Dr. Goel said it’s evident that testing will not keep new variants out of the country. With vaccines protecting air travellers from severe disease, a better use of the country’s limited testing resources would be random testing throughout the community to strengthen surveillance systems, he said.
Lisa Barrett, an infectious disease specialist and professor at Dalhousie University, said there is little point in testing every air traveller now because the virus is “everywhere.” However, testing at airports remains an important tool with which to monitor new variants.
“Places and spaces where people move are still good places to track the virus,” she said. “That does not mean that we need to use PCR [tests] all the time in the usual way, but we might want to take a sampling of PCR tests at those sites.”
If a country signalled that a new variant of concern had been detected, testing one out of every 10 passengers from that country could help Canada pick up on early signals, Dr. Barrett cited as an example. Travellers could also take those tests home to streamline the process at the airport.
“I don’t think there’s a defensible reason why we wouldn’t keep that surveillance present,” she said.
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