A record proportion of fully vaccinated overseas travelers discovered they had contracted COVID-19 through the mandatory PCR test at the airport, data released by the federal government for December shows.
Among the passengers who arrived in Canada during the week following Christmas and who were obliged to undergo a second screening test for COVID-19 upon arrival, one in 20 had the unpleasant surprise of learning of their infection with the virus. And this, even if it is mandatory to be adequately vaccinated and to show proof of a first negative PCR test dating back less than three days to board a plane.
“We see that the positivity rates [mesurés aux frontières] have been increasing for several weeks. This demonstrates the importance of the measures we have taken at our borders to protect the health and safety of Canadians, “said D.r Howard Njoo, Deputy Chief Administrator of Federal Public Health.
Ottawa reintroduced mandatory testing on arrival for air travelers arriving from a country other than the United States on May 1is December, in order to slow down the entry into the country of the Omicron variant. In mid-December, when the federal government decided to officially advise against foreign travel, only a fraction of one percent of those tests came back positive.
However, the positivity rates drastically increased between the weeks of December 12 (0.74%), December 19 (2.26%) and December 26 (4.93%), according to latest summary data from the Public Health Agency of Canada.
At least 5,000 people carrying the virus were identified through an airport test, between December 26 and December 1 alone.is January, out of the 101,013 travelers tested at the airport during this period.
Consequence of Omicron
« [Ce taux de positivité] is huge. It follows the trend of the Omicron variant, it started to explode with its arrival, ”says Benoit Barbeau, virologist and professor in the Department of Biological Sciences at the University of Quebec in Montreal.
He explains this situation by the fact that vaccination seems less effective in preventing infection with the Omicron variant than with the original strain of the COVID-19 virus. The variant would also develop a viral load more quickly, which could thwart the first PCR test, carried out abroad, he believes.
“Going from zero viral load to high viral load can be quite fast. If three days [avant l’arrivée], you test negative, it is more likely to be a false negative with Omicron. »
The specialist was until very recently ambivalent about the merits of the obligation of a second test on arrival. In light of the most recent data, he now says he believes in the usefulness of this measure, which could notably help slow the arrival in the country of other variants, such as a sub-variant of Omicron.
Still useful, judges Public Health
Earlier this week, Air Canada, WestJet and Toronto’s Pearson Airport called on the Trudeau government to end the mandatory second PCR test imposed on travelers arriving in the country. The office of federal health minister Jean-Yves Duclos says such a relaxation is not expected in the short term and that Public Health advises him to maintain the PCR test on arrival.
“It is also very important for monitoring [de l’évolution de la pandémie], says the Dr Njoo. He is not [uniquement] issue of diagnosis [la maladie chez] travelers individually, but also to detect perhaps a new variant. It’s part of our border screening program. »
The positivity rate is even higher for tests performed at the land border between Canada and the United States. More than 12% of swabs collected from randomly selected vaccinated travelers during the week following Christmas revealed the presence of the virus. This rate climbs to nearly 19% among the 1,927 partially vaccinated or unvaccinated people who crossed the border during the same week, as essential workers.
By way of comparison, the positivity rate of the PCR tests carried out in screening centers in Quebec among the general population also experienced a significant increase during the month of December, peaking at more than 30% in the first days of January.