People who have had COVID-19 may be protected against getting it again for at least five months, a new study has shown.
The results from the Public Health England study revealed that antibodies from a past coronavirus infection provide 83% protection against reinfection during that time.
But crucially, experts said, that some people could still catch it and may be able to transmit it to others.
But early results showed that between 18 June and 24 November, there were 44 potential reinfections (2 “probable” and 42 “possible” reinfections) out of 6,614 participants who had tested positive for antibodies.
Some of those workers had COVID-19 symptoms during the first wave of the virus in the spring but were not PCR tested then.
Professor Susan Hopkins, Senior Medical Advisor at Public Health England and the SIREN study lead, said that those who previously had COVID-19 likely would not have a severe case if reinfected.
"This means even if you believe you already had the disease and are protected, you can be reassured it is highly unlikely you will develop severe infections but there is still a risk that you could acquire an infection and transmit to others," Hopkins said.
"Now more than ever it is vital we all stay at home to protect our health service and save lives," she added.
The SIREN (Sars-Cov-2 Immunity & REinfection EvaluatioN) study from Public Health England has regularly tested more than 20,000 healthcare workers at 102 NHS trusts since June.
These early results of the study were released in preprint and have not yet been peer-reviewed.
Researchers will continue to look into antibodies and the possibility of reinfection. Scientists are also trying to figure out how long the approved coronavirus vaccines protect against the virus.
Further research is also underway to determine whether antibodies protect against the new, more transmissible variant of coronavirus in the UK.
It comes as the country rolls out a mass vaccination campaign and is in the midst of its third national lockdown.
The country has recorded staggering numbers of daily deaths in the past weeks as officials warn that Europe may be in the most acute phase of the pandemic.