Retrospective SARS-CoV-2 IgG screening during the first wave (March-June 2020) of the COVID-19 pandemic in the United Kingdom

During the "first wave" of the coronavirus disease 2019 (COVID-19) pandemic in the United Kingdom (March-June 2020), the city of Leicester was particularly hard hit, resulting in reimposed lockdown measures. Although initial polymerase chain reaction testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was attempted within the community, testing was soon abandoned due to an inability to keep up with demand by local laboratories. It is therefore feasible that undiagnosed transmission of COVID-19 in the community by asymptomatic individuals was a real possibility. Therefore, retrospective SARS-CoV-2 immunoglobulin G (IgG) testing of archived sera from out-patients visiting University Hospitals of Leicester NHS Trust service was performed to investigate the transmission of SARS-CoV-2 in the community. A total of 1779 sera samples were tested from samples collected between 16th March and 3rd June 2020, of which 202 (11.35%) were SARS-CoV-2 IgG positive. Positivity was lowest in March (2.54%) at the beginning of the pandemic before peaking in April (17.16%) before a decline in May and June (11.16% and 12.68%, respectively). This retrospective screening offers some insight into the early patterns of SARS-CoV-2 transmission within a sampled community population during the first wave of the COVID-19 pandemic; supporting the argument for more community screening during high incidences of pandemics.