Condition category
Infections and Infestations
Date applied
Date assigned
Last edited
Retrospectively registered
Overall trial status
Recruitment status

Plain English Summary

Background and study aims
COVID-19 is a condition caused by the coronavirus (called SARS-CoV-2) that was first identified in late 2019. This virus can infect the respiratory (breathing) system. Some people do not have symptoms but can carry the virus and pass it on to others. People who have developed the condition may develop a fever and/or a continuous cough among other symptoms. This can develop into pneumonia. Pneumonia is a chest infection where the small air pockets of the lungs, called alveoli, fill with liquid and make it more difficult to breathe.

In 2020, the virus has spread to many countries around the world and neither a vaccine against the virus or specific treatment for COVID-19 has yet been developed. As of March 2020, it is advised that people minimize travel and social contact, and regularly wash their hands to reduce the spread of the virus.

Groups who are at a higher risk from infection with the virus, and therefore of developing COVID-19, include people aged over 70 years, people who have long-term health conditions (such as asthma or diabetes), people who have a weakened immune system and people who are pregnant. People in these groups, and people who might come into contact with them, can reduce this risk by following the up-to-date advice to reduce the spread of the virus.

Understanding people's immunity to COVID-19 is key to controlling the virus and informing how we deal with potential future waves. SIREN is investigating whether people can be re-infected by the SARS-CoV-2 virus that causes COVID-19 and therefore if someone can catch COVID-19 more than once.

The aim is to find out whether healthcare workers test positive for COVID-19 more than once, or whether they test positive for COVID-19 even though they have some immunity.

Who can participate?
Healthcare workers aged 18 years or older, who work with patients in a clinical setting can take part

What does the study involve?
When someone joins the study they provide a blood sample and a nose and throat swab. The blood sample tests for antibodies, which indicate someone has some immunity to COVID-19, and the nose and throat swab tests for the virus. These two tests indicate whether someone has ever had COVID-19 (a positive blood test), or whether they have it right now (a positive nose and throat swab).
Every two weeks, healthcare workers will do a nose and throat swab and complete a questionnaire about any exposure to the virus and any symptoms they have. Every four weeks a blood sample will be taken to test whether they have any immunity. Participants will be followed for one year and may be asked to provide extra samples, if additional tests are needed to determine whether they may have been re-infected.

What are the possible benefits and risks of participating?
The study will not benefit participants directly but will help provide important information about SARS-CoV2 re-infection among staff working in healthcare organisations and provide a stronger evidence base to inform national guidance and policy.

For some, blood sampling may cause momentary discomfort at the site of the blood draw, possible bruising, redness, and swelling around the site, bleeding at the site, feeling of lightheadedness when the blood is drawn, and rarely, an infection at the site of blood draw. Some individuals may find the swab tests uncomfortable. The study is following ethical guidance to ensure that the volume of blood taken is within safe limits.

Where is the study run from?
The study run by Public Health England in collaboration with a number of Universities. Over 100 NHS Trusts are participating in the study, which is where samples are taken.

When is the study starting and how long is it expected to run for?
May 2020 to March 2022

Who is funding the study?
The Department for Health and Social Care (UK)

Who is the main contact?
Dr Susan Hopkins,

Trial website

Contact information



Primary contact

Dr Susan Hopkins


Contact details

Public Health England
Wellington House
United Kingdom
+44 (0)207 7940500

Additional identifiers

EudraCT number

Nil known number

Nil known

Protocol/serial number

IRAS 284460

Study information

Scientific title

Sarscov2 Immunity & REinfection EvaluatioN: Impact of detectable anti-SARS-COV2 on the subsequent incidence of COVID-19 in healthcare workers



Study hypothesis

Prior COVID-19 infection with the subsequent detection of SARS-CoV-2 is protective against future clinical and asymptomatic infection

Primary objective:
To determine whether the presence of antibody to SARS-CoV-2 (anti-SARS-CoV-2) is associated with a reduction in the subsequent risk of re-infection over short term periods (reviewed monthly) and the next year.

Ethics approval

Approved 22/05/2020, Berkshire Research Ethics Committee (East Hampstead Baptist Church, South Hill Road, Bracknell, RG12 7NS, UK; +44 (0)2071048224;, ref: 20/SC/0230

Study design

Prospective observational cohort study

Primary study design


Secondary study design

Cohort study

Trial setting


Trial type


Patient information sheet

Not available in web format, please use contact details to request a copy of the participant information sheet


COVID-19 (SARS-CoV-2 infection)


Upon enrolment, participants will complete an online questionnaire and provide a blood sample for antibody testing and swabs for viral testing. Thereafter, every two to four weeks participants will be asked to provide further swab samples and complete a follow-up questionnaire to provide information on possible COVID-19 symptoms, exposures and enrolment in vaccine or treatment trials. On a monthly basis, participants will also be asked to provide further blood samples for serological testing.. Participants will be followed up for 12 months from their enrolment.

The samples will be tested in local Trust labs but will also be used for central confirmatory antibody testing and serological characterisation, or for viral genome sequencing and/or culture.

Intervention type



Drug names

Primary outcome measure

1. SARS-CoV-2 antibody measured in NHS laboratories using local assays (Roche Cobas or Abbott Platforms) measured monthly
2. SARS-CoV-2 infection measured using PCR test using local assays measured every two weeks

Secondary outcome measures

1. Symptoms of SARS-Cov-2 infection measured by a 2 weekly survey of participants developed and validated by study team including the 12 most commonly reported symptoms
2. Ability to culture viable virus from SARS-CoV-2 residual viral samples that are PCR positive submitted to PHE throughout the study, cultured in category 3 laboratory on vero cells
3. Identification of reinfection or persistent infection if second positive test after 90 days measured using SARS-CoV-2 viral RNA submitted to COG-UK sequencing laboratories for each positive PCR result
4. Serological response measured using SARS-CoV-2 residual positive sera submitted to PHE and measured using laboratory assays monthly
5. Serological response measured using enzyme immunoassay detection of IgG measured using laboratory assays monthly
6. NHS Trust, age, sex, staff group, ethnicity and co-morbidities as recorded by the participant recorded at baseline using a novel questionnaire
7. Phylogenetic relatedness of SARS-CoV-2 whole genome sequences on positive PCR samples, linked to MRC CLIMB in a secure data infrastructure with other samples submitted from hospitals and community in the same time period

Overall trial start date


Overall trial end date


Reason abandoned (if study stopped)


Participant inclusion criteria

Hospital healthcare worker willing to consent for regular follow up for 12 months with swabs and blood samples

Participant type

Health professional

Age group




Target number of participants

Minimum 10,000 Maximum 100,000

Participant exclusion criteria

Unwilling to participate in regular follow up

Recruitment start date


Recruitment end date



Countries of recruitment

United Kingdom

Trial participating centre

Royal Free Hospital
Royal Free London NHS Trust Pond St
United Kingdom

Sponsor information


Public Health England

Sponsor details

Wellington House
United Kingdom
+44 (0)1980 612922

Sponsor type




Funder type


Funder name

Department of Health and Social Care

Alternative name(s)

Department of Health & Social Care, DH

Funding Body Type

government organisation

Funding Body Subtype

National government


United Kingdom

Results and Publications

Publication and dissemination plan

Planned publication in a high-impact peer-reviewed journal.

IPD sharing statement:
The current data sharing plans for this study are unknown and will be available at a later date.

2020 protocol (not peer reviewed) in (added 08/01/2021)

Intention to publish date


Participant level data

To be made available at a later date

Basic results (scientific)

Publication list

Publication citations

Additional files

Editorial Notes

05/01/2021: Trial’s existence confirmed by National Institute for Health Research (NIHR).