COVID-19 Home Test Kit, containing sealed test tube and swab, security seal sticker, letter about the study, return label and instructions, instruction booklet, biohazard disposal bag and flat packed return cardboard box, produced as part of the Real-time Assessment of Community Transmission (REACT-1) study conducted by Imperial College London and the polling company Ipsos Mori, UK, 2021

In a pandemic, a major challenge for scientists is to track how disease is spreading. Between May 2020 and June 2021, nearly two million people from every part of England got involved in the REACT-1 study by taking an at home PCR (polymerase chain reaction) test.

The REACT-1 study was commissioned by the Government in April 2020 and has been run monthly since then. Each month, 150,000 people are randomly chosen from across England and invited to take part. If they chose to be involved, they are sent a PCR test in the post to complete and return. Scientists can then see how many people in this large sample test positive for COVID-19. This data is then used to estimate how many people overall have COVID-19 at that point. The large sample size means that it is possible to track COVID-19 even when there are a relatively low number of cases.