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New study casts doubt on effectiveness of COVID-19 border closures

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A new study comparing data from 166 countries that closed their borders during the first 22 weeks of the pandemic says most targeted closures – aimed at travellers from COVID-19 hotspots – did little to curb the crisis.

By contrast, total border closures barring all non-essential travel did slow the spread of COVID-19, but at such a high cost that the writers warn they should only be considered in the future as a last resort.

The report was published Feb. 28 in the medical journal PLOS Global Public Health by researchers from York University's Global Strategy Lab, and looked at both global and country-level impacts of closures.

“People just assumed at the time that these measures were effective, but that’s not necessarily the case,” the paper’s lead author, Mathieu Poirier, said in a media release. Poirier is a social epidemiology professor at York and co-director of the Global Strategy Lab.

“Our study shows, using real-world data, that for most countries, in most situations, border closures are not going to be the best approach," he said.

Beginning in late January and throughout February 2020, some countries placed restrictions on foreign travellers from countries with high rates of COVID-19 transmission. Then, when the World Health Organization declared the pandemic on March 11, so many countries closed their borders to all non-essential travel that the study estimates at least 95 per cent of the world’s population was affected by border closures.

On a global level, the study found that early wave of targeted closures had no impact on global COVID-19 transmission, while early total border closures did manage to reduce the rate of transmission globally.

"While the global sum of targeted border closures implemented by Feb. 5, 2020 were not sufficient to slow the COVID-19 pandemic, the global sum of total border closures implemented by March 19, 2020 did result in a statistically significant reduction in global COVID-19 transmission," the study reads.

Researchers found that targeted closures were no more likely to reduce COVID-19 transmission domestically than globally.

Of the 34 countries they studied that enacted targeted closures, 12 experienced decreased transmission, 10 experienced increased transmission and 12 experienced mixed results.

Total closures produced slightly better domestic results. Of the 103 countries that closed their borders to all non-essential travel, 41 experienced reduced transmission, 28 experienced increased transmission and 34 experienced mixed results.

The reasons why targeted border restrictions failed to significantly curb transmission during the pandemic have been explored in other studies as well.

According to one study published in the Canadian Medical Association Journal in June 2022, restrictions aimed at travellers from South Africa during the Omicron surge in 2021 failed to prevent the variant from spreading in Canada because by then, it was already spreading in Europe.

That same study called Canada one of the strictest G10 countries in limiting international and domestic travel.

The federal government closed its international borders to foreign nationals, excluding Americans, on March 16, 2020, in an effort to limit the number of cases entering the country. A few days later, Canada and the United States announced a joint decision to close their shared border to all but essential travel.

According to the York University study, this placed Canada among the countries that managed to curb COVID-19 transmission in the first 22 weeks of the pandemic through total border closures. However, a study published by researchers at the University of British Columbia in August 2023 found that the longer the closures remained, the less they benefited Canadians.

The study, published in the peer-reviewed journal eLife, revealed that the number of COVID-19 cases entering Canada dropped 10-fold four weeks after restrictions barring the entry of most foreign nationals took effect.

However, these restrictions did not prevent all COVID-19 cases from entering the country, and by then, the virus was already circulating here. Despite border closures, SARS-CoV-2 continued to spread within Canada during the spring and summer of 2020, seeding new chains of transmission that would feed the second wave of COVID-19 that fall.

“Travel restrictions have a diminishing return if domestic transmission is high, if highly transmissible variants become widespread globally, or if there are many individuals exempt from travel restrictions and quarantine without access to rapid testing,” the study's lead author, Angela McLaughlin, said in a media release.

If restrictions had been kept at their maximum for longer, with fewer exceptions, the researchers said, they could have held off more transmission, but this would have come at a steep cost.

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

The authors of the York University study agree. While total border closures were more likely to curb the transmission of COVID-19 both domestically and globally, the social and economic disruptions they caused were so significant, they said, that those closures should only be used as a last resort.

"Governments that…cannot feasibly implement less restrictive alternatives might consider enacting border closures," the authors wrote.

"However, given their moderate and uncertain impacts and their significant harms, border closures are unlikely to be the best policy response for most countries and should only be deployed in rare circumstances and with great caution."

 With files from CTVNews.ca writer Alexandra Mae Jones 

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