A single on-arrival antigen test is as effective as a ten-day self-isolation period in reducing imported cases of Covid-19, new modelling has argued.

Based on prevalence rates at home and abroad and accounting for quarantine compliance, Oxera and Edge Health find that a single rapid antigen test would be appropriate for arrivals from the majority of countries categorised as medium risk, where there are medium caseloads or lower vaccination rates.

Such countries could be designated as ‘amber’ if the UK government applies a traffic light system for foreign travel to categorise risk.

In evidence submitted to the global travel taskforce this week, many of the quick, inexpensive and effective antigen tests are shown to reduce the number of infectious days of an international arrival by 63 per cent.

This means that the risk of community transmission from a single test is comparable, if not more effective, to a ten-day quarantine period with no testing, which screens 62 per cent of infectious days and was the UK border policy for countries without travel corridors until January 18th.

The new findings demonstrate how the government’s evidence base has underestimated the effectiveness of a single antigen test, which SAGE previously reported would screen only 11 per cent of infectious travellers.

For higher-risk countries, a two-test strategy could be a viable option as part of a risk-based framework to safely reopen international travel this summer.

Using a 72-hour pre-departure antigen test and three-day quarantine with PCR test, 87 per cent of potentially infectious days are screened – just one percentage point lower than a dual-PCR test.

Crucially, the new evidence demonstrates that the two-test approach delivers effective levels of screening, while ensuring that the UK can easily track and genome sequence the tests of passengers, mitigating the risk of importing variants of concern.

Michele Granatstein, partner at Oxera, said: “The ultimate goal for governments must be to return to frictionless travel between countries that are considered lower-risk.

“The vaccine roll-out, combined with internationally agreed standards on digital solutions to evidence Covid-status certification, will be intrinsic to that, but people should be able to travel safely, with or without a vaccine.”

Virgin Atlantic chief executive, Shai Weiss, welcomed the news.

He said: “We believe that international travel can safely restart at scale, using a risk-based, phased easing of testing requirements and border restrictions, that follows the scientific evidence.

“In parallel to the world-leading UK vaccination programme, seamless travel between the UK and lower risk countries – such as the US, Caribbean and Israel – must remain the objective, enabling the free movement of people and goods that are vital to the economic recovery.

“When applied to the government’s proposed traffic light framework, this new modelling by Oxera and Edge Health demonstrates how robust and proportionate testing strategies can be applied to amber and red countries, protecting public health by reducing imported infections and capturing variants of concern early through genomic sequencing.”