PHE study finds people who have had COVID-19 can still transmit the virus

A study from Public Health England (PHE) has found that although people who have had COVID-19 may have immunity against the virus for ‘at least five months’, they could still be able to transmit it to others.

The SIREN study has been regularly performing antibody and PCR testing on healthcare workers from 102 NHS trusts since June 2020.

The study found that antibody protection after infection lasts for at least five months on average, although the researchers are currently studying whether protection may last for longer.

They also found evidence that those with antibodies could still carry the novel coronavirus in their nose and throat and spread it to other people.

The SIREN study scientists also detected 44 potential cases of COVID-19 reinfections between 18 June and 24 November 2020.

Within the study, of these potential reinfection cases, two were deemed ‘probable’ while 42 were determined to be ‘possible’ based on the confirmatory evidence available to researchers.

The PHE experts added that if all 44 cases were confirmed, it would represent an 83% rate of protection from reinfection. On the other hand, if only the two ‘probable' reinfections are confirmed, the rate would rise to 99%.

Additional research is currently ongoing to clarify the range of protection from reinfection, and also to continue to assess whether protection may last longer than the current estimation of at least five months.

“This study has given us the clearest picture to date of the nature of antibody protection against COVID-19 but it is critical that people do not misunderstand these early findings,” said Susan Hopkins, senior medical advisor at PHE and lead of the SIREN study.

“We now know that most of those who have had the virus, and developed antibodies, are protected from reinfection, but this is not total and we do not yet know how long protection lasts. Crucially, we believe people may still be able to pass the virus on.

“This means that even if you believe you've already had the disease and are protected, you can be reassured it is highly unlikely you will develop severe infection but there is still a risk that you could acquire an infection and transmit it to others,” she added.

The new findings highlight the need for people to limit their contact with others, with the R number currently above one across the country.