Repeated mass testing of staff and residents in prison outbreaks of Covid-19: an enhanced outbreak investigation in two adult prisons in England, 2021

BackgroundThe management of Covid-19 outbreaks presented particular challenges in the prison setting. In this study we describe the results from the implementation of a serial mass testing approach in two adult prisons in northern England. The overall aim was to examine the epidemiology of Covid-19 outbreaks in prisons and help inform public health policy and practice during the pandemic. MethodsRepeat mass testing was offered to all eligible staff and residents in a womens (nresidents=239; nstaff=246) and a mens (nresidents=703; nstaff=340) prison in February and March 2021 at days 0, 7 and 28 after Covid-19 outbreaks were declared. Positive swab samples were sent for viral whole genome sequencing by COG-UK. FindingsParticipation in at least one testing round ranged from a low of 67% of staff in the mens prison to a high of 98% of residents in the womens prison. The largest outbreak, in the mens prison (261 cases in residents and 37 cases in staff), continued to see new cases identified at the last testing round on day 28. Test positivity in residents of both prisons was significantly lower (p<0.05) at day 28 than on preceding test days, but no significant difference was observed for staff (p>0.05). Epidemiological data in conjunction with sequencing information provided evidence for multiple introductions of the SARS-CoV-2 virus from the local community into the prisons, with transmission identified both within wings and between wings among residents and staff. Two distinct SARS-CoV-2 lineages were identified in the womens and mens prisons, B.1.177 and B.1.17, respectively. ConclusionsDuring a Covid-19 outbreak, timely implementation of a whole prison testing regime can serve to inform a targeted approach to infection prevention and control by identifying the true extent of disease transmission in all (including asymptomatic) individuals. Staff, in particular, should be tested regularly and testing uptake should be as high as possible to minimise the risk of infection incursion. Ensuring high testing uptake across all testing rounds remains a challenge.