By James Simons-
Most people who have had Covid-19 are protected from catching it again for at least five months, a study led by Public Health England shows.
PHE England 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 say 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.
The report concluded that past infection was linked to an 83% lower risk of getting the virus, compared with those who had never had Covid-19, scientists found.
Between 18 June and 24 November, scientists detected 44 potential reinfections (2 ‘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 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:
”This study has given us the clearest picture to date of the nature of antibody protection against COVID-19 but it is critical people do not misunderstand these early findings.
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 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. Now more than ever it is vital we all stay at home to protect our health service and save lives.
We are immensely grateful to our colleagues in the NHS for giving up their time to volunteer, and whose continued participation at a time of great stress is making this research possible.
Prof Susan Hopkins, who led the study, said the results were encouraging, suggesting immunity lasted longer than some people feared, but protection was by no means absolute.
From June to November 2020, almost 21,000 healthcare workers across the UK were regularly tested to see whether they: Of those who had no antibodies to the virus, suggesting they had never had it, 318 developed potential new infections within this timeframe, the tests indicated.
They will also look closely at cases with the new variant – which was not widespread at the time of this first analysis – and observe the immunity of participants who receive the vaccine.
Dr Julian Tang, a virus expert at the University of Leicester, said the results were reassuring for healthcare workers.
“Having the vaccine after recovering from Covid-19 is not an issue… and will likely boost the natural immunity,” he added.
“We also see this with the seasonal flu vaccine.
“So hopefully the results from this paper will reduce the anxiety of many healthcare-worker colleagues who have concerns about getting Covid-19 twice.”