Testing for COVID-19 during an outbreak within a large UK prison: an evaluation of mass testing to inform outbreak control.

• Systematic mass testing in closed settings provides information on infection rates. • Test positivity was 11.6%, with only one-quarter reporting symptoms. • The prison wing handling new admissions reported the second-lowest positivity rate. • Testing uptake was higher in residents than in staff members. • Mass testing is a valuable tool to bring outbreaks under control quickly. The aim of this paper was to describe the results of mass asymptomatic testing for COVID-19 in a male prison in England following the declaration of an outbreak. It provides novel data on the implementation of a mass testing regime within a prison during the pandemic. The paper is an observational evaluation of the mass testing conducted for 6 months following the declaration of a COVID-19 outbreak within a prison. It investigated the incidence of positive cases in both staff and residents using polymerase chain reaction testing. Data from October 2020 until March 2021 was included. A total of 2170 tests were performed by 851 residents and 182 staff members; uptake was 48.3% for people living in prison and 30.4% for staff. Overall test positivity was 11.6% (14.3% for residents, 3.0% for staff), with around one-quarter of these reporting symptoms. The prison wing handling new admissions reported the second-lowest positivity rate (9.4%) of the eight wings. Mass testing for COVID-19 over a short space of time can lead to rapid identification of additional cases, particularly asymptomatic cases. Testing that relies on residents and staff reporting symptoms will underestimate the true extent of transmission and will likely lead to a prolonged outbreak. [ABSTRACT FROM AUTHOR]