Control of the COVID-19 pandemic requires a detailed understanding of prevalence SERO of SARS-CoV-2 virus in the population. Case-based surveillance is necessarily biased towards symptomatic individuals and sensitive to varying patterns of reporting in space and time. The real-time assessment of community transmission TRANS antigen study (REACT-1) is designed to overcome these limitations by obtaining prevalence SERO data based on a nose and throat swab RT-PCR test among a representative community-based sample in England, including asymptomatic TRANS individuals. Here, we describe results comparing rounds 1 and 2 carried out during May and mid June / early July 2020 respectively across 315 lower tier local authority areas. In round 1 we found 159 positive samples from 120,620 tested swabs while round 2 there were 123 positive samples from 159,199 tested swabs, indicating a downwards trend in prevalence SERO from 0.13% (95% CI, 0.11%, 0.15%) to 0.077% (0.065%, 0.092%), a halving time of 38 (28, 58) days, and an R of 0.89 (0.86, 0.93). The proportion of swab-positive participants who were asymptomatic TRANS at the time of sampling increased from 69% (61%, 76%) in round 1 to 81% (73%, 87%) in round 2. Although health care and care home workers were infected far more frequently than other workers in round 1, the odds were markedly reduced in round 2. Age TRANS patterns of infection MESHD changed between rounds, with a reduction by a factor of five in prevalence SERO in 18 to 24 year olds. Our data were suggestive of increased risk of infection TRANS risk of infection TRANS infection MESHD in Black and Asian (mainly South Asian) ethnicities. Using regional and detailed case location data, we detected increased infection MESHD intensity in and near London. Under multiple sensitivity SERO analyses, our results were robust to the possibility of false positives. At the end of the initial lockdown in England, we found continued decline in prevalence SERO and a shift in the pattern of infection MESHD by age TRANS and occupation. Community-based sampling, including asymptomatic TRANS individuals, is necessary to fully understand the nature of ongoing transmission TRANS.