M. Pollán, B. Pérez-Gómez, R. Pastor-Barriuso, J. Oteo, M. Hernán, M. Pérez-Olmeda, J. L. Sanmartín, A. Fernández-García, I. Cruz, N. Fernández de Larrea, M. Molina, Francisco Rodríguez-Cabrera, Mariano Martín, P. Merino-Amador, José León Paniagua, J. F. Muñoz-Montalvo, F. Blanco, R. Yotti, Faustino Rodrigo Mariano Saturnino Marta Juan F. Matías Jos Blanco Gutiérrez Fernández Martín Mezcua Navarro M, F. Blanco, Rodrigo Gutiérrez Fernández, Mariano Martín, Saturnino Mezcua Navarro, M. Molina, J. F. Muñoz-Montalvo, Matías Salinero Hernández, J. L. Sanmartín, M. Cuenca‐Estrella, R. Yotti, José León Paniagua, N. Fernández de Larrea, P. Fernández-Navarro, R. Pastor-Barriuso, B. Pérez-Gómez, M. Pollán, A. Avellón, G. Fedele, A. Fernández-García, Jesus Oteo Iglesias, María Teresa Pérez Olmeda, I. Cruz, M. E. Fernandez Martinez, Francisco Rodríguez-Cabrera, M. Hernán, Susana Padrones Fernández, J. Rumbao Aguirre, J. M. Navarro Marí, B. Palop Borrás, A. Pérez Jiménez, M. Rodríguez-Iglesias, Ana María Calvo Gascón, María Luz Lou Alcaine, I. Donate Suárez, Óscar Suárez Álvarez, M. Rodríguez Pérez, Margarita Cases Sanchís, Carlos Javier Villafáfila Gomila, L. Carbo Saladrigas, A. Hurtado Fernández, A. Oliver, Elías Castro Feliciano, María Noemí González Quintana, José María Barrasa Fernández, María Araceli Hernández Betancor, M. Hernández Febles, L. Martín Martín, Luis-Mariano López López, Teresa Ugarte Miota, Inés de Benito Población, María Sagrario Celada Pérez, M. N. Vallés Fernández, Tomás Maté Enríquez, Miguel Villa Arranz, M. Domínguez-Gil González, I. Fernández-Natal, Gregoria Megías Lobón, J. L. Muñoz Bellido, P. Ciruela, Ariadna Mas i Casals, Maria Doladé Botías, M. Á. Marcos Maeso, D. Pérez del Campo, Antonio Félix de Castro, Ramón Limón Ramírez, Maria Francisca Elías Retamosa, M. Rubio González, María Sinda Blanco Lobeiras, Alberto Fuentes Losada, A. Aguilera, G. Bou, Yolanda Caro, Noemí Marauri, Luis Miguel Soria Blanco, I. del Cura González, M. Hernández Pascual, R. Alonso Fernández, P. Merino-Amador, N. Cabrera Castro, Aurora Tomás Lizcano, C. Ramírez Almagro, M. Segovia Hernández, N. Ascunce Elizaga, M. Ederra Sanz, C. Ezpeleta Baquedano, Ana Bustinduy Bascaran, Susana Iglesias Tamayo, Luis Elorduy Otazua, Rebeca Benarroch Benarroch, Jesús Lopera Flores, A. Vázquez de la Villa
The Lancet, 2020
Summary Background Spain is one of the European countries most affected by the COVID-19 pandemic. Serological surveys are a valuable tool to assess the extent of the epidemic, given the existence of asymptomatic cases and little access to diagnostic tests. This nationwide population-based study aims to estimate the seroprevalence of SARS-CoV-2 infection in Spain at national and regional level. Methods 35 883 households were selected from municipal rolls using two-stage random sampling stratified by province and municipality size, with all residents invited to participate. From April 27 to May 11, 2020, 61 075 participants (75·1% of all contacted individuals within selected households) answered a questionnaire on history of symptoms compatible with COVID-19 and risk factors, received a point-of-care antibody test, and, if agreed, donated a blood sample for additional testing with a chemiluminescent microparticle immunoassay. Prevalences of IgG antibodies were adjusted using sampling weights and post-stratification to allow for differences in non-response rates based on age group, sex, and census-tract income. Using results for both tests, we calculated a seroprevalence range maximising either specificity (positive for both tests) or sensitivity (positive for either test). Findings 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, with a specificity–sensitivity range of 3·7% (3·3–4·0; both tests positive) to 6·2% (5·8–6·6; either test positive), with no differences by sex and lower seroprevalence in children younger than 10 years (<3·1% by the point-of-care test). There was substantial geographical variability, with higher prevalence around Madrid (>10%) and lower in coastal areas (<3%). Seroprevalence among 195 participants with positive PCR more than 14 days before the study visit ranged from 87·6% (81·1–92·1; both tests positive) to 91·8% (86·3–95·3; either test positive). In 7273 individuals with anosmia or at least three symptoms, seroprevalence ranged from 15·3% (13·8–16·8) to 19·3% (17·7–21·0). Around a third of seropositive participants were asymptomatic, ranging from 21·9% (19·1–24·9) to 35·8% (33·1–38·5). Only 19·5% (16·3–23·2) of symptomatic participants who were seropositive by both the point-of-care test and immunoassay reported a previous PCR test. Interpretation The majority of the Spanish population is seronegative to SARS-CoV-2 infection, even in hotspot areas. Most PCR-confirmed cases have detectable antibodies, but a substantial proportion of people with symptoms compatible with COVID-19 did not have a PCR test and at least a third of infections determined by serology were asymptomatic. These results emphasise the need for maintaining public health measures to avoid a new epidemic wave. Funding Spanish Ministry of Health, Institute of Health Carlos III, and Spanish National Health System.
Cited by 717 publications.
Field of study: Medicine