Updated 29 May: The Office for National Statistics has found that around 7% of a random sample of the population have antibodies to SARS-CoV-2, the virus which causes COVID-19. Blood samples were tested from 885 people from randomly selected private households since 26 April. This low level of people who have naturally developed antibodies to the virus is too low to rely on herd immunity protecting the population.
Published 22 May: The Health and Social Care Secretary, Matt Hancock, announced that results of the monitoring of antibody development in the population shows "around 17% of people in London, and around 5% or higher in the rest of the country, have tested positive for coronavirus antibodies." Testing for antibodies so far has been carried out in a targeted fashion, and the plan is to have much wider testing. The first phase will be increased testing of "health and care staff, patients and residents". As knowledge of the antibody response increases, the aim is to "develop the systems of certification to ensure people who have positive antibodies can be given assurance about what they can safely do."