December 22, 2021

expert reaction to self-isolation period for COVID-19 cases being reduced from 10 to 7 days following two negative LFDs on days 6 and 7

The UK Health Security Agency (UKHSA) has announced new guidance that allows the 10-day self-isolation period for COVID-19 cases to be reduced to 7 days following negative Lateral Flow Device (LFD) tests.

Dr Richard Tedder, member of the Clinical Virology Network, said:

“Overall this is a compromise based on the supposition that a previously infected person who is not shedding viral proteins, in other words has two negative Lateral Flow Device (LFD) tests, is unlikely to transmit coronavirus to contacts.  On a balance of probabilities this is probably correct.  Reservations still hold for self administered LFDs and how a negative result is validated.  The requirement for two sequential LFDs is a good compromise.  Such assays are far less sensitive than PCR but it is likely that the low level of virus shed by a person who returns a negative LFD, but who might have a positive PCR, would not be a source of virus transmission.  That said, the reagents used in LFDs must be kept under scrutiny as the antigenic changes in the viral proteins that are likely to occur as the virus continues to evolve in the human population might lead to loss of reactivity with the LFD.  A second reservation is that these recommendations should apply only to those persons who are not known to be immunosuppressed by concurrent illness or therapy where the kinetics of viral shedding may be different.”

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