Negative test after seven days could be get-out-of jail-free card for those self isolating
Cutting the self-isolation requirement for people who have come into contact with a Covid-19 case from 14 days to seven days, with a test at that point, could be as effective as the current system, according to a new study in the Lancet Public Health.
A "test to release" system which would allow people with a negative test result to stop isolating after seven days would prevent the same amount of transmission as the current World Health Organization-recommended 14-day period, the modelling study from the London School of Hygiene and Tropical Medicine found (LSHTM).
The UK government currently stipulates a 10-day self-isolation period for contacts of known coronavirus cases. However, there are concerns over compliance, with some studies suggesting only 11 per cent of people made it to the full two weeks before it was shortened to 10 days in December.
Researchers at LSHTM were more generous, assuming that 50 per cent of people completed the full 14-day period, preventing 59 per cent of Sars-CoV-2 transmission.
However, a similar result could be reached with only seven days of quarantine followed by a test, the study found, assuming a similar level of compliance. At that point, those who tested negative would be allowed to stop isolating, while positive cases would have to remain indoors, as would those experiencing symptoms at any point.
The researchers also suggested similar results could be achieved by cutting self-isolation entirely, and replacing it with daily tests for five days.
However, they stressed that more research was needed in a real-world context, and urged people to comply with the existing rules. They also called for better support for those who have to self-isolate.
Julian Tang, associate professor of virology at the University of Leicester, said that test, track and trace strategies were only successful if quarantine was strictly enforced.
"The approach modelled in this study could improve compliance theoretically, but it may be difficult to implement such timely testing and result reporting in the real world. And even with the testing, without enforcement, people may still break seven-day quarantine - if they feel the need to do so," said Prof Tang, who was not involved in the study.
"Also the variable incubation - two to 14 days - for Covid-19 may still allow some with negative tests on day seven to become infectious later and infect others," he said.
Professor Mark Woolhouse, an epidemiologist at the University of Edinburgh who was also not involved in the study, said: "Even if testing is not quite as effective as a period of quarantine, if compliance is higher, it can more than outweigh the difference. In the long run, this will be an important part of us accepting we are living with the virus and finding ways to do that which are sustainable."
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