Study finds past coronavirus (COVID-19) infection provides some immunity for at least five months, but people may still carry and transmit the virus.
People infected with COVID-19 in the past are likely to be protected against reinfection for several months, a Public Health England (PHE) study has found, although experts cautioned those with immunity may still be able carry the virus in their nose and throat and therefore have a risk of transmitting to others.
PHE has been regularly testing tens of thousands of health care workers across the UK since June for new COVID-19 infections as well as the presence of antibodies, which suggest people have been infected before.
SIREN study leaders are clear this first report provides no evidence towards the antibody or other immune responses from COVID-19 vaccines, nor should any conclusions to be drawn on their effectiveness. The SIREN study will consider vaccine responses later this year.
PHE scientists working on the study have concluded naturally acquired immunity as a result of past infections provide 83% protection against reinfection, compared to people who have not had the disease before. This appears to last at least for 5 months from first becoming sick.
While the SIREN study will continue to assess whether protection may last for longer, this means people who contracted the disease in the first wave may now be vulnerable to catching it again.
Between 18 June and 24 November, scientists detected 44 potential reinfections (two ‘probable’ and 42 ‘possible’ reinfections) out of 6,614 participants who had tested positive for antibodies. This represents an 83% rate of protection from reinfection.
PHE also warned that although those with antibodies have some protection from becoming ill with COVID-19 themselves, early evidence from the next stage of the study suggests that some of these individuals carry high levels of virus and could continue to transmit the virus to others.
It is therefore crucial that everyone continues to follow the rules and stays at home, even if they have previously had COVID-19, to prevent spreading the virus to others. Remember to wash hands regularly, wear face coverings and make space from others to help reduce the likelihood of passing on the virus.
It is vital that, with cases at their highest level to date and the R number above 1 across the country, people do everything that they can to avoid the risk of transmitting the virus to other people.
Professor Susan Hopkins, Senior Medical Advisor at Public Health England and the SIREN study lead said: