In January 2020, Elsevier created a free COVID-19 resource centre with information in English and Mandarin. The centre is hosted on Elsevier Connect, providing access to research on the novel coronavirus. Elsevier grants permission for free access to its research in PubMed Central and other repositories for unrestricted reuse. A nationwide, population-based study in Spain (ENE-COVID) estimated the seroprevalence of SARS-CoV-2 infection. The study involved 61,075 participants, with 75.1% of contacted individuals participating. Participants underwent a point-of-care antibody test and, if agreed, donated blood for further testing. Seroprevalence was 5.0% (95% CI 4.7–5.4) by the point-of-care test and 4.6% (4.3–5.0) by immunoassay. The specificity-sensitivity range was 3.7% (3.3–4.0) to 6.2% (5.8–6.6). There was significant geographical variation, with higher prevalence in Madrid and lower in coastal areas. Around a third of seropositive participants were asymptomatic, and only 19.5% of symptomatic participants reported a previous PCR test. The study highlights the need for maintaining public health measures to prevent a new epidemic wave. The findings emphasize that most of the Spanish population is seronegative, with a substantial proportion of infections being asymptomatic. The study used two tests to estimate seroprevalence, with the point-of-care test showing good performance compared to the immunoassay. The results provide valuable data for public health policies and underscore the importance of serological surveys in understanding the spread of the virus. The study was funded by the Spanish Ministry of Health, the Institute of Health Carlos III, and the National Health System.In January 2020, Elsevier created a free COVID-19 resource centre with information in English and Mandarin. The centre is hosted on Elsevier Connect, providing access to research on the novel coronavirus. Elsevier grants permission for free access to its research in PubMed Central and other repositories for unrestricted reuse. A nationwide, population-based study in Spain (ENE-COVID) estimated the seroprevalence of SARS-CoV-2 infection. The study involved 61,075 participants, with 75.1% of contacted individuals participating. Participants underwent a point-of-care antibody test and, if agreed, donated blood for further testing. Seroprevalence was 5.0% (95% CI 4.7–5.4) by the point-of-care test and 4.6% (4.3–5.0) by immunoassay. The specificity-sensitivity range was 3.7% (3.3–4.0) to 6.2% (5.8–6.6). There was significant geographical variation, with higher prevalence in Madrid and lower in coastal areas. Around a third of seropositive participants were asymptomatic, and only 19.5% of symptomatic participants reported a previous PCR test. The study highlights the need for maintaining public health measures to prevent a new epidemic wave. The findings emphasize that most of the Spanish population is seronegative, with a substantial proportion of infections being asymptomatic. The study used two tests to estimate seroprevalence, with the point-of-care test showing good performance compared to the immunoassay. The results provide valuable data for public health policies and underscore the importance of serological surveys in understanding the spread of the virus. The study was funded by the Spanish Ministry of Health, the Institute of Health Carlos III, and the National Health System.