The 14-day quarantine rules are likely preventing less than one coronavirus case a week from reaching the UK from the EU or US, research suggests.
The issue of self-isolating after an overseas trip is a controversial topic.
While the UK Foreign Office has lifted its “all but essential” travel restriction for many destinations, a rise in coronavirus cases in Spain prompted officials to reinstate a 14-day self-isolation for holidaymakers returning from the country.
Spain’s prime minister Pedro Sánchez has called the move, which affects people travelling from anywhere in the nation, “unjust”, arguing only Catalonia and its neighbouring region Aragón have seen a dramatic spike in transmissions.
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Despite widespread criticism for the blanket nature of the decision, Boris Johnson is sticking by it, arguing that “swift and decisive action” is needed in areas where cases are “bubbling up”.
A timely study by the London School of Hygiene and Tropical Medicine (LSHTM) suggests a shorter quarantine period, combined with a coronavirus test, would likely be similarly effective.
Shorter quarantines ‘still prevent substantial transmission’
The scientists noted that long quarantine periods may have financial implications for those who are unable to work from home, while others could be put off travelling altogether, affecting the tourism industry.
Some may also be reluctant to self-isolate if the period feels unnecessarily long.
“People should only quarantine for as long as they need to,” said study author Dr Sam Clifford.
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To better understand how travel quarantines stem the spread of infection, the LSHTM scientists used EU flight data to simulate travellers arriving in the UK from Europe or the US.
Findings suggest an eight-day quarantine combined with a coronavirus swab on day seven – allowing 24 hours for the results to come through – would reduce the number of infectious travellers entering communities by around 94%, compared with if no isolation was in place.
The scientists noted this is “similar to that achieved by a 14-day quarantine period”, which was found to reduce the integration of coronavirus-positive arrivals by around 99%.
The preliminary results were published on the online research site Medrxiv and are yet to appear in a peer-reviewed journal.
Experts have argued a coronavirus test would be required seven days into a potential infection, rather than at an airport, due to the pathogen’s incubation period – the time between catching it and showing symptoms.
While the results support some degree of self-isolation, the scientists stressed “requiring a 14-day quarantine period likely results in less than one infectious traveller each entering the UK per week from the EU and the USA”.
“Shorter quarantine periods still can prevent a substantial amount of transmission,” they wrote.
“All strategies in which travellers spend at least five days in quarantine and have at least one negative test before release are highly effective.”
Early research suggests the coronavirus tends to cause symptoms within five days of infection.
While the proposed model would mean some coronavirus patients still enter the UK, this would be unlikely to contribute to a dreaded second wave.
“One or two cases getting in isn’t going to be the end of the world,” said study author Professor John Edmunds.
“You obviously don’t want it, [but] it won’t change the epidemiology in the UK.”
Shorter quarantines ‘very significantly benefit travel industry’
The scientists also found that without any isolation requirements, up to 23 infectious travellers would integrate into UK communities from the US a week. This is given the US’s existing prevalence of 40 patients per 10,000 people.
Up to a dozen patients would arrive from the EU if quarantining was not in place.
The transmission risk on arrival was found to be highest among travellers not yet showing symptoms.
“Quarantine policies will shift this risk increasingly towards asymptomatic infections if eventually-symptomatic individuals self-isolate after the onset of symptoms,” wrote the scientists.
“As passenger numbers recover, strategies to reduce the risk of re-introduction should be evaluated in the context of domestic [coronavirus] incidence, preparedness to manage new outbreaks, and the economic and psychological impacts of quarantine.”
Professor Mark Woolhouse from the University of Edinburgh called the study a “welcome illustration of the principle that testing can be used to reduce the need for quarantine”, but stressed it relied on “assumptions”.
“One scenario not considered in this paper is testing at arrival and again a few days later,” he said.
“It is possible that a double testing strategy could be almost as effective as 14 days quarantine.”
Dr Andrew Freedman, an honorary consultant physician, added the results provide a “strong argument in favour of shortening the quarantine period from the current 14 days to eight days”, alongside a swab on day seven.
“This would have a very significant benefit to the individual traveller as well as the travel industry as a whole,” he said.
“It remains to be seen whether the UK government will be willing to adopt such a strategy.”