Information on COVID-19 reinfection surveillance in England
Updated 16 March 2021
Applies to England
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COVID-19 reinfection
When you get infected with a virus, you usually gain some protection against further infection (reinfection) from the same virus through your immune system – this is called immunity and can be short-lived or long lasting. Immunity can also mean that you could still get infected with the same virus but may be protected against severe disease.
We are still at a relatively early point in the COVID-19 pandemic regarding opportunities for reinfection and limited cases have been published worldwide. We do not currently know very much about people that have already been infected with SARS-CoV-2 (the virus that causes COVID-19 disease) and who then get reinfected. It is, therefore, important that possible cases of reinfection are followed up as far as possible in a standard way, so that each case can be categorised using agreed criteria. This will allow us to look at how long immunity lasts, protection against clinical disease (disease with symptoms) and protection against more severe disease. It is also important to understand whether those who become reinfected can pass the virus on to other people.
Reinfection can occur with other human coronaviruses and has been reported from around 6 months after the first infection. A study (Lumley et al 2020) of over 12,000 people working in 4 English hospitals found that people who developed antibodies after SARS-CoV-2 infection were protected against disease for 6 months after infection and reinfection (without any disease symptoms) was very rare.
Similarly, a UK Biobank study found 88% of 1,699 people with antibodies against COVID-19 still had these antibodies up to 6 months later. The SIREN study detailed below has also published similar findings. As more information is published on these studies and surveillance we will update these pages to link to new research.
Investigation and management of suspected SARS-CoV-2 reinfections is set out in the guide for clinicians and infection specialists.
Public Health England’s role in investigating reinfection
Public Health England (PHE) is working with other groups and coordinating different studies and surveillance protocols to investigate whether it is possible for people who have previously tested positive for SARS-CoV-2 infection to get infected again. These areas of surveillance and research are described below.
National surveillance of possible reinfection
As part of PHE’s COVID-19 surveillance, all SARS-CoV-2 testing undertaken in the hospital setting (pillar 1) and within the wider community (pillar 2) in England is reported to PHE. This data is examined on a regular basis to identify people who may have had 2 separate episodes of COVID-19 based on positive test results.
People with 2 positive samples taken at least 90 days apart – and with no positive tests in-between – are contacted either directly by email (pillar 2 cases), or information has been requested via the microbiologists at the testing laboratory (pillar 1 cases).
The aim of this surveillance is to identify any repeat episodes of COVID-19 disease in people in England, to bring together these data on a national level and to offer support for further investigation to local laboratories. Data generated from this surveillance has already informed the 90-day interval between positive test results in the definition of possible reinfection.
PHE surveillance of people with possible reinfection based on national testing data
PHE is following up everyone who is a possible reinfection if their second test was reported through community testing (pillar 2). Anyone contacted directly by PHE will be asked to fill out a short online survey with questions on their symptoms and reasons for testing. This information will be used to understand more about how often reinfection occurs and how people with possible reinfection are affected by the virus.
These data are collected under Section 60 of the Health and Social Care Act 2001 (now subsumed into the National Information Governance Board for Health and Social Care, with Section 60 now Section 251 of the NHS ACT 2006).
The survey answers will help us to find people who have had symptomatic illness with both COVID-19 episodes. These people may then be offered a home kit to collect samples for further testing to help confirm or rule out a diagnosis of reinfection.
The original regulations in England were developed for testing people with symptoms and assumed that people would clear the infection quite quickly. We now know that that people can carry on being PCR positive for much longer than was originally thought, which is why a minimal interval of 90 days is used to look for possible reinfections. The prolonged positive assay appears to be due to detection of viral fragments that are no longer infectious.
Further information is available for participants.
COVID-19 Genomics UK
The COVID-19 Genomics UK (COG-UK) is a partnership of NHS organisations, public health agencies of all 4 UK nations, Wellcome Sanger Institute and academic partners. The consortium uses whole genome sequencing to carry out a variety of research.
A combination of samples is tested, from those identified as clusters or outbreak investigations; those from special groups of patients and community surveillance by selecting a subset of positive samples identified as part of pillar 2 testing. Genome sequences are then compared with other samples in the UK and the GISAID database to look for emerging sequences and where possible to look for sequence differences between samples taken from the same person at different times to look for evidence of potential reinfection in people with different COVID-19 strains. Further information is available on COG-UK.
The SIREN study of healthcare workers
PHE’s ‘SIREN’ (SARS-CoV-2 Immunity and REinfection EvaluatioN) study has recruited thousands of NHS workers from across the UK to investigate whether specific COVID-19 antibodies provide immunity. This study will follow people for at least 12 months with regular testing. Further information is available on the SIREN study. The SIREN study found 83% protection against reinfection, compared to people who have not had the disease before. Protection was found to be even higher against the reinfection that makes you ill. This protection appears to last for at least 5 months from first becoming infected – these findings have been published.
Vivaldi care home study
The Vivaldi study aims to provide a detailed picture of coronavirus infection in care homes in England. These findings will help improve understanding of these vulnerable groups’ immune response to COVID-19 and help inform future treatments for the virus.
As part of the major research study led by University College London (UCL), 14,000 care home residents and staff will be tested quarterly for their immune response to COVID-19. Around 340 care homes are taking part, testing approximately 4,500 residents and 9,500 staff. Further information on the Vivaldi study is available here.