| Interventions |
Workflow 1: Retrospective study of SARS-CoV-2 seroprevalence across the UK using surplus serum samples. Using the Roche Elecsys assay the researchers will test >7500 serum samples from IBD patients for SARS-CoV-2 antibodies. These include: i) surplus serum samples from UK therapeutic drug monitoring laboratories retained since 09/02/2020 and ii) serum samples from patients recruited to the UK NIHR IBD Bioresource project from 01/12/2019 to 30/03/2020. For each sample the supplier of the sample (the therapeutic drug monitoring laboratory or the UK NIHR IBD Bioresource) will provide the age and sex of the patient, the date of the serum sample, the drug tested and the name of the referring hospital. No other patient identifiers will be provided to ensure these samples will be anonymous to the research team. Patient consent for SARS-CoV-2 antibody testing will not be sought and no study visits are required. Workflow 2: 40-week prospective observational UK-wide study of SARS-CoV-2 seroprevalence in IBD patients receiving infliximab or vedolizumab. In parallel the researchers will conduct a prospective observational study of 6970 patients receiving infliximab or vedolizumab in UK infusion units. This study is specifically designed to determine whether anti-TNF therapy (with or without an immunomodulator) impacts SARS-CoV-2 seroprevalence, the magnitude/durability of serological responses and the proportion of patients who acquire PCR positive COVID-19 after seroconversion. A comparator group will comprise patients receiving vedolizumab. Current data suggests that vedolizumab, a gut selective anti-integrin a4 monoclonal antibody, is not associated with an increased risk of systemic infection or pneumonia. Furthermore, it is administered in hospital at the same 8 weekly in |