A total of 250 healthcare workers are currently off sick with symptoms of SARS-CoV-2 infection (COVID-19) while 99 additional members of staff have been diagnosed with confirmed SARS-CoV-2 at Great Ormond Street Hospital. As a consequence, all routine surgery, out-patient activity and day cases have been postponed or cancelled altogether. It is therefore critical for us to understand whether or not this disease will continue to threaten staff health or whether natural infection will give rise to long lasting immunity.

This is a 2-arm prospective cohort study recruiting at least 1000 healthcare workers at GOSH over 6 years.Staff will be recruited and coordinated from each department to be representative of the full diversity of healthcare workers at the Trust. The age distribution of the participants will be monitored on a weekly, basis against the known age distribution of the hospital to ensure that the sample is representative.

Trust communications team will send an all staff email to inform them about this research project asking them to get in touch with the study team if they wish to participate and they meet the basic eligibility criteria. Potential participants will be asked voluntarily to attend a face to face appointment in person (or if preferred by telephone or 1:1 video teleconference meeting) to enable trained study staff to seek informed consent before they enter the study. Informed consent will be undertaken by study staff who are Good Clinical Practice trained, Human Tissue Act trained, study trained, GOSH consent trained and registered in the study log.

The consent process will specifically cover the reason for the study, the storage of samples and agreement for future samples to be tested once improved testing is made available. Once the member of staff has provided informed consent, they will be asked to undertake an online questionnaire in which they will record demographic details including age, sex, email address and telephone contact for results and coordinating follow up. The questionnaire will also record details of SARS-CoV-2 like symptoms, contact with SARS-CoV-2, pre-existing co-morbidities and medication or treatments that may interfere with serological testing.

After providing informed consent, the staff members then be asked attend the study phlebotomy testing clinic. Appointments will be 20 minutes in length but actual blood sampling for serological testing will be 5-10 minutes to allow plenty of time and space for staff members to be tested to maintain social distancing. A total of 8ml of blood will be stored for testing.

Follow up sampling and questionnaires of approximately 200 staff members with PCR confirmed SARS-CoV-2 infected staff will take place monthly. While follow up of all ~800 asymptomatic staff members will take place 6 monthly. All staff will continue to have access to the GOSH PCR COVID19 testing program (as they do at present). This will enable us to confirm with PCR testing any new (or reinfected) positive staff member with COVID-19 over the duration of the study.

When initially asymptomatic seronegative staff become serologically positive during the course of the study, they will remain under active surveillance but they will switch arms of the study and they will contribute to the active follow up of serologically positive patients.

If staff leave the GOSH NHS trust during the study they will still be eligible to remain in the study and be followed up and we will update their contact details on the follow-up questionnaire.

After the initial intensive phase, all approximately 1000 recruits will be followed 6 monthly for the 6 year duration of the study. Follow-up visits will be arranged following the baseline assessment. The same blood tests 4ml EDTA and 4ml serum will be taken at each follow up appointment as well as the same symptom questionnaire.