We obtained an overall IFR estimate and estimates stratified by age and sex15. the authors estimate that 6% of adults in England had been infected by mid-July 2020, with health and long-term care workers and those of Black or South Asian ethnicity disproportionately affected. Introduction England has experienced a large outbreak of SARS-CoV-2 contamination leading to the highest excess mortality in Europe by June 20201. The first recorded COVID-19 death occurred on 28 February, with in-hospital deaths peaking by mid-April2. Hospital admission and mortality data show an asymmetrical burden of COVID-19 in England, with high rates in older people and those living in long-term care, and in people of minority ethnic groups, particularly Black and Asian (mainly South Asian) individuals3C6. It is unclear how much of this excess is due to differences in exposure to the virus, e.g. related to workplace exposures and structural inequality, and how much is due to differences in outcome, including access to health care7C9. As part of the UK Governments response to controlling the spread of the virus, on March 23 it announced a national lockdown that prohibited all but essential activities. The UK came out of lockdown from mid-May as restrictions were gradually eased as more business were allowed to reopen and TNFAIP3 the public was encouraged to use face coverings Salvianolic acid A in situations Salvianolic acid A when social distancing could not be maintained. Antibody data provide a long-lasting measure of SARS-CoV-2 contamination, enabling analyses of the timing and extent of the recent epidemic. Most infected people mount an Salvianolic acid A IgG antibody response detectable after 14C21 days although levels may start to wane after ~90 days10. Uncertain validity of the available antibody assessments, inconsistencies in sampling methods, small numbers and use of selected groups have made many studies difficult to interpret11. Different acceptability criteria may apply to community-based studies where population-wide results are required than for studies focused on individual risk11C14. While not generally Salvianolic acid A approved for individual care, self-administered lateral flow immunoassay (LFIA) tests done at home provide a means for obtaining reliable community-wide prevalence estimates rapidly and at scale, at affordable cost15,16, by adjusting the results for known test performance17. Here, we obtained estimates of the cumulative community prevalence of IgG antibodies for SARS-CoV-2 contamination among a representative sample of over 100,000 adults aged over 18 years in England, and specific sub-groups of the population, e.g. by ethnicity and occupation, to mid-July 202018. We used home-based self-testing with a LFIA that had been extensively evaluated for sensitivity and specificity in both laboratory and clinic settings and for acceptability and usability among the public19,20. The assessments were delivered by post to randomly selected individuals who were given detailed instructions (including by video) on how to carry out the procedure. Participants were asked to upload a photograph of the completed test and to complete a brief questionnaire either online or by telephone (see the Methods section and published protocol18). As well as measuring community prevalence and identifying groups at most risk of contamination, we estimated the total number of infected individuals in England and the contamination fatality ratio (IFR) overall and by age, sex and ethnicity. Results Of the 121,976 people who were sent test kits, 109,076 (89.4%) completed the questionnaire of whom 105,651 Salvianolic acid A (96.9%) completed the test, during the period 20 JuneC13 July 2020; 5544 (5.2%) were IgG positive, 94,364 (89.3%) IgG unfavorable and 5743 (5.4%) reported an invalid or unreadable result, giving a crude prevalence of 5.6% (95% CI 5.4C5.7). After adjusting for the performance characteristics of the test and re-weighting to be representative of the population, overall antibody prevalence was 6.0% (95% CI: 5.8C6.1). This equates to 3.36 (3.22, 3.51) million adults in England who had antibodies to SARS-CoV-2 in England to mid-July 2020. Prevalence was highest at ages 18C24 years (7.9%, 95% CI 7.3, 8.5) and in London (13.0%, 95% CI 12.3, 13.60) (Supplementary Table?1). Highest prevalence by ethnic group was.