Health Life

Modelling study estimates impact of ‘test to release’ strategy for contacts of COVID-19 cases

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Quarantine time after contact with a confirmed COVID-19 case could potentially be reduced to 7 days without raising the risk of onward transmission of the virus by testing people on the seventh day of quarantine with either a PCR or lateral flow antigen (LFA) test, findings from an English modeling study published today in The Lancet Public Health journal suggest.

The study, which accounts for infected people’s potential viral load and the sensitivity of COVID-19 tests, estimates that people who test negative after 7 days of quarantine are unlikely to be infectious and could potentially be released without raising the risk of onward virus transmission above what would be expected by quarantining for 14 days without testing.

Daily testing for 5 days after exposure to COVID-19 using rapid lateral flow kits could potentially avert a similar level (50%) of onward virus transmission as the 14-day approach without the need to quarantine at all, if individuals isolate when receiving a positive test, the model predicts.

The study does not evaluate the number or cost of tests that would be required for this approach, however. The authors stress that people should continue to observe the official guidance on quarantine and self-isolation, which the UK government has set at 10 days, until their findings can be verified with further research.

Assistant Professor Sam Clifford, joint-lead author and member of the CMMID COVID-19 Working Group at the London School of Hygiene & Tropical Medicine, says: “Adherence to quarantine rules is key for reducing onward COVID-19 transmission. Our findings suggest that incorporating testing of contacts into a trace-isolate system could potentially help to reduce quarantine times, and this in turn may improve adherence by making it easier to complete the full isolation period. Our study did not evaluate costs, however, and