15 January 2021
Initial reports from the national SIREN study say that antibodies from past COVID-19 infection provide 83% protection against reinfection for at least 5 months. The study was designed to understand whether prior infection with SARS-CoV2 (the virus that causes COVID-19) protects against future infection with the same virus. It has been led by Public Health England (PHE) and UHNM has taken part in the innovative programme.
Public Health England has been regularly testing tens of thousands of healthcare 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.
250 staff signed up to take part in the study at UHNM, which requires participants to present for fortnightly testing for Covid-19.
Dr Chris Duff, Consultant Clinical Scientist, and SIREN Principal Investigator at UHNM said: “These initial findings from the SIREN study show how research is giving us better understanding of whether past COVID-19 infection may provide some protection against future reinfection. I’m thrilled that hundreds of staff volunteered to take part, and thank them for their on-going commitment to this research. Running SIREN has required huge effort by teams across the Trust, involving many staff across Research & Innovation, Pathology and Phlebotomy, and I would like to recognise their continued hard work in making it possible for us to conduct this important research at UHNM.”
So far UHNM has processed nearly 1,000 antibody tests and nearly 1,500 swab PCR tests for SIREN since Sept from 250 staff.
Reinfections in people with antibodies were rare, with experts identifying 44 potential reinfections among 6,614 participants who showed evidence of previous infection. However, experts have 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 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 five 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.
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.”
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.
Public Health England continues to stress the importance of following the stay at home rules and remembering hands, face, space – whether you have had the virus or not.
- Public Health England’s SIREN (SARS-CoV-2 Immunity & Reinfection EvaluatioN) study has performed regular antibody and PCR testing on 20,787 healthcare workers, including frontline clinical staff and those in non-clinical roles, from 102 NHS trusts since the study commenced in June. 6,614 of these participants tested positive for COVID-19 antibodies upon recruitment.
- Of the 44 potential reinfections identified by the study, 2 were designated “probable” and 42 “possible”, based on the amount of confirmatory evidence available. If all 44 cases were confirmed, it would represent an 83% rate of protection from reinfection, while if only the two “probable” reinfections were confirmed, the rate would be 99%. Further research is ongoing to clarify this range.
- The study found that antibody protection after infection lasts for at least five months, on average, and scientists are currently studying whether protection may last for longer. This means that many people who contracted the disease in the first wave may now be vulnerable to catching it again.
- Both of the two “probable” reinfections reported having experienced COVID-19 symptoms during the first wave of the pandemic, but were not tested at the time. Both patients reported that their symptoms were less severe the second time. None of the 44 potential reinfection cases were PCR tested during the first wave, but all tested positive for COVID-19 antibodies at the point of recruitment to the study.
- This analysis occurred prior to the widespread dissemination of the new variant VOC202012/01, further work is underway in the laboratory to understand whether and to what extent antibodies also provide protection from this variant and future analysis will assess the impact of VOC202012/01 on symptomatic and asymptomatic infections in healthcare workers.
- The study will continue to follow participants for 12 months to explore how long any immunity may last, the effectiveness of vaccines and to what extent people with immunity are able to carry and transmit the virus.