Travel restrictions sharply reduced COVID-19 entry into Canada early in pandemic, but didn’t stop new outbreaks: study

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A new study looking at the first and second waves of the pandemic in 2020 and 2021 says travel restrictions preventing entry to Canada dramatically reduced the number of COVID-19 cases entering the country.

However, the researchers say, it still wasn’t enough to stop further outbreaks.

In the study, published Tuesday in the peer-reviewed journal eLife, researchers at the University of British Columbia analyzed public data on viral genome sequences collected in 2020 and early 2021 to find the geographic source of specific chains of COVID-19 transmission. 19.

They found that four weeks after Canada restricted the entry of most foreign nationals in March 2020, the number of COVID-19 cases crossing the border into the country had dropped 10-fold.

“COVID-19 imports accelerated in the run-up to March 2020, but experienced a sharp and dramatic decline after travel restrictions were implemented,” Angela McLaughlin, a bioinformatics doctoral candidate, said in a press release. at UBC and lead author of the study. release.

“The data shows that federal travel restrictions can be effective in reducing viral importations when implemented quickly.”

But COVID-19 was already here and travel restrictions couldn’t stop it.

The spring and summer of 2020 saw daily case levels at one of the lowest nationally, but circulation was still occurring within the country, the study described, with specific chains of transmission persisting into fall 2020.

As travel restrictions were relaxed in November 2020, allowing more entry into the country and shortening quarantine requirements, the international importation of COVID-19 cases rebounded.

Concerning variants, starting with the Alpha variant, began to arrive in Canada. The researchers estimated that 30 unique genetic sublineages of the Alpha variant, also known as B.1.1.7, had entered the country by the end of February 2021.

Numerous factors, such as the state of the global fight against COVID-19, including the appearance of these variants in other parts of the world, make it difficult for travel restrictions to have an impact later in the pandemic, the researchers said.

“Travel restrictions have diminishing returns if domestic transmission is high, if highly transmissible variants become globally widespread, or if there are many people exempt from travel and quarantine restrictions without access to rapid testing,” says McLaughlin.

On March 21, 2020, in response to the pandemic, the US and Canada mutually closed the border to recreational travel after previously closing their borders to most non-citizens seeking to enter the country.

One month after these restrictions, the researchers found that imports of COVID-19 decreased from 58.5 sublineages of the virus on average per week to just 10.3 times less in four weeks.

There were still “newly seeded sub-lineages” throughout the summer of 2020 as national broadcasting continued. Travel restrictions were slightly relaxed in the fall, although the US land border did not reopen to non-essential travel until August 2021.

During the first wave of the pandemic in early 2020, 49 percent of COVID-19 viral importations into Canada likely came from the US, the study found, entering primarily through Quebec and Ontario.

The United States remained the largest international source of COVID-19 for Canada in the second wave, according to the data, at 43 percent. Cases from India accounted for 16 per cent of those who came from outside the country in the second wave, while cases from the UK accounted for seven per cent.

If the restrictions had been kept at their maximum for longer, they might have prevented further transmission, the researchers postulated, but this would have had consequences in other areas.

“The social and economic repercussions of travel restrictions must be weighed against the risk of unrestricted viral importations, which have the potential to overwhelm the health care system,” Mclaughlin said.

“We are now in the era of infectious disease,” Dr. Jeffrey B. Joy, an assistant professor in the UBC department of medicine and lead author of the study, said in the statement. “This study highlights the growing importance of genomic epidemiology, enabled by the sharing of genomic sequence data, to inform and evaluate public health policies to combat current and future viral outbreaks that threaten society.”

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