Daily Rapid Lateral Flow COVID-19 Tests for Traced Contacts for Five Days Could Replace Requirement to Quarantine, Reveals Study

Additional testing with either a PCR or lateral flow antigen (LFA) test could potentially reduce the quarantine time of contacts of a confirmed case to seven days from the WHO recommended 14-day quarantine period without raising the risk of onward transmission, according to a new modeling study.

Researchers at the London School of Hygiene & Tropical Medicine (LSHTM; London, UK) conducted the study using mathematical modeling to estimate the effect of different quarantine and testing strategies on reducing onward transmission from traced secondary infections. The team simulated the levels of virus an infected person would be likely to produce at each stage of infection, alongside timing of symptom onset, test sensitivity and tracing and testing timings. The team estimate that completing the full 14-day recommended quarantine period for contacts of COVID-19 cases could prevent 59% of onward virus transmission. A similar proportion of onward transmission could potentially be prevented with only seven days of quarantine if a PCR or LFA test is performed on the final day of quarantine and people who receive a negative result are released.

The study estimates that the quarantine period could be replaced if traced contacts are required to take a daily LFA test for five days and those who do not receive any positive results are released, with 50% of onward virus transmission predicted to be prevented. If people adhere perfectly to self-isolation for the recommended 14 days after a positive test, and their close contacts taking a daily LFA test for five days and are then released on the final day if all tests are negative, the model estimates 80% of onward virus transmission could potentially be averted. Notably, the model is based on the assumption that the LFA test works at the higher level of sensitivity, detecting on average 76.8% of cases that tested positive in a PCR test.

“Our findings suggest that introducing testing of contacts in contact tracing may allow for a large reduction in the duration of quarantine,” said Billy Quilty, joint-lead author and Research Assistant at LSHTM. “Daily rapid tests for at least five days may allow for the quarantine requirement to be removed entirely, with self-isolation required only upon the onset of symptoms or a positive rapid test result. This strategy may allow for critical essential workers to continue working if exposed but not infected.”

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London School of Hygiene & Tropical Medicine (LSHTM)