Implementation of novel and conventional outbreak control measures in managing a COVID-19 outbreak in a large UK prison

Background: SARS-CoV-2 can spread rapidly within correctional facilities. On 22nd March 2020, following identification of a confirmed COVID-19 case in a prisoner in Prison A (UK), an Outbreak Control Team was convened consisting of prison staff and public health experts from Public Health England and the UK National Health Service. Methods: At the start of the outbreak, four prisoners and 40 staff were isolating with COVID-19 symptoms. An outbreak was declared and full prison lockdown implemented. Prompt implementation of novel outbreak control measures prevented an explosive prison outbreak, specifically establishment of dedicated isolation and cohorting units, including (i) Reverse Cohorting Units (RCUs) for accommodating new detainees; (ii) Protective Isolation Units (PIUs) for isolating symptomatic prisoners (new detainees and existing residents), and (iii) Shielding Units (SUs) to protect medically vulnerable prisoners. Findings: In total, 120 probable and 25 confirmed cases among prisoners and staff were recorded between March and June 2020. Among prisoners, there were six possible, 79 probable, and three confirmed cases. Among staff, there were 83 possible, 79 probable, and 22 confirmed cases. Testing of symptomatic prisoners was limited for most of the outbreak, with only 33% of probable cases tested. This explains the low number of confirmed cases (three) among prisoners despite the large number of probable cases (n=81; 92%). Over 50% of the initial cases among prisoners were on the two wings associated with the index case. Interpretation: Rapid transmission of SARS-COV-2 was prevented through proactive steps in identifying and isolating infected prisoners (and staff), cohorting new admissions and shielding vulnerable individuals. These novel and cost-effective approaches can be implemented in a wide range of correctional facilities globally and proved effective even in the absence of mass testing.