There is insufficient scientific evidence to know whether the presence of SARS-CoV-2 antibodies confers protection from subsequent infections, and if so at what level. Antibodies are only one part of the immune response to infection. Tests that detect SARS-CoV-2 antibodies are available. They can determine whether someone has had COVID-19. Tests can reveal those who are unaware that they had COVID-19 because they had mild or no symptoms. Test samples must be analysed in a laboratory – no home tests are authorised for use in the UK. The Government provides antibody tests for NHS and social care staff, hospital patients and care home residents. Commercial test kits are available for private use. These are of varying quality and results must be interpreted with caution. A positive test does not necessarily mean that someone will be protected from subsequent infections. There are concerns that access to private tests of variable quality will discourage the public from practising effective public health measures. Antibody tests are an important tool to understand the spread of the virus and how many people in a population have been infected. They are being used in infection surveillance surveys in the UK and elsewhere.