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

ABSTRACT

Background: The 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. Methods: Repeat mass testing was offered to all eligible staff and residents in a women's (nresidents=239; nstaff=246) and a men's (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. Findings: Participation in at least one testing round ranged from a low of 67% of staff in the men's prison to a high of 98% of residents in the women's prison. The largest outbreak, in the men's 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). Aggregate data from the women's prison indicated that approximately 30% of resident cases had Covid-19 symptoms when tested. 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 women's and men's prisons, B.1.177 and B.1.17, respectively. Conclusions: During 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.