UKHSA estimates one in seven still infectious after five day COVID-19 isolation

One in seven people who have tested positive for COVID-19 could still be infectious, if released from isolation upon receiving a negative lateral flow device (LFD) result after five days, new data suggests.

Presently, individuals self-isolating in the UK are allowed to leave on day seven, provided they have tested negative on two lateral flow tests in the past 24 hours, and do not have a fever. However, the Prime Minister Boris Johnson has indicated that he is in favour of further reducing the quarantine time to five days, if backed by scientific evidence.

A new report – not based on data specific to the Omicron variant – researched a number of isolation periods, including five days of self-isolation followed by five lateral flow tests on days five to nine, with self-isolation ending after a single negative test result. 
‘This increased the proportion of people infectious when released from self-isolation from 5% to 15%,’ the study reported.

A previous study shared by the UK Health Security Agency (UKHSA) estimated that after ten full days of self-isolation, 5% of people who tested positive for SARS-CoV-2 are still infectious. However, ‘reducing the ten-day isolation period to seven days, with two consecutive negative LFD test results from day six means an estimated 6% of people are still infectious when ending self-isolation,’ the UKHSA shared. ‘The proportion of people estimated to remain infectious five days after symptom onset or a positive test is 31% and at 14 days it is 1%.’

The London School of Hygiene and Tropical Medicine has found evidence that ‘the number of infectious days in the community can be reduced to almost zero’ by requiring at least two consecutive days of negative lateral flow tests, ‘regardless of the number of days’ wait until testing again after initially testing positive’.