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Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study.
Lancet. 2020 08 22; 396(10250):535-544.Lct

Abstract

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.

Authors+Show Affiliations

National Centre for Epidemiology, Institute of Health Carlos III, Madrid, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Institute of Health Carlos III, Madrid, Spain. Electronic address: mpollan@isciii.es.National Centre for Epidemiology, Institute of Health Carlos III, Madrid, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Institute of Health Carlos III, Madrid, Spain.National Centre for Epidemiology, Institute of Health Carlos III, Madrid, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Institute of Health Carlos III, Madrid, Spain.National Centre for Microbiology, Institute of Health Carlos III, Madrid, Spain; Spanish Network for Research in Infectious Diseases (REIPI), Institute of Health Carlos III, Madrid, Spain.Department of Epidemiology, Harvard T H Chan School of Public Health, Boston, MA, USA; Department of Biostatistics, Harvard T H Chan School of Public Health, Boston, MA, USA; Harvard-MIT Division of Health Sciences and Technology, Boston, MA, USA.National Centre for Microbiology, Institute of Health Carlos III, Madrid, Spain.Deputy Directorate of Information Technologies, Ministry of Health, Madrid, Spain.Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Institute of Health Carlos III, Madrid, Spain; Department of Clinical Microbiology, Hospital Clínico San Carlos, Madrid, Spain.National School of Public Health, Institute of Health Carlos III, Madrid, Spain.National Centre for Epidemiology, Institute of Health Carlos III, Madrid, Spain; Consortium for Biomedical Research in Epidemiology and Public Health (CIBERESP), Institute of Health Carlos III, Madrid, Spain.General Secretary of Health, Ministry of Health, Madrid, Spain.National School of Public Health, Institute of Health Carlos III, Madrid, Spain.Deputy Directorate of Information Technologies, Ministry of Health, Madrid, Spain.Department of Clinical Microbiology, Hospital Clínico San Carlos, Madrid, Spain.General Secretariat, Institute of Health Carlos III, Madrid, Spain.Deputy Directorate of Information Technologies, Ministry of Health, Madrid, Spain.General Secretary of Health, Ministry of Health, Madrid, Spain.Directorate, Institute of Health Carlos III, Madrid, Spain.No affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

32645347

Citation

Pollán, Marina, et al. "Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a Nationwide, Population-based Seroepidemiological Study." Lancet (London, England), vol. 396, no. 10250, 2020, pp. 535-544.
Pollán M, Pérez-Gómez B, Pastor-Barriuso R, et al. Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study. Lancet. 2020;396(10250):535-544.
Pollán, M., Pérez-Gómez, B., Pastor-Barriuso, R., Oteo, J., Hernán, M. A., Pérez-Olmeda, M., Sanmartín, J. L., Fernández-García, A., Cruz, I., Fernández de Larrea, N., Molina, M., Rodríguez-Cabrera, F., Martín, M., Merino-Amador, P., León Paniagua, J., Muñoz-Montalvo, J. F., Blanco, F., & Yotti, R. (2020). Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study. Lancet (London, England), 396(10250), 535-544. https://doi.org/10.1016/S0140-6736(20)31483-5
Pollán M, et al. Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a Nationwide, Population-based Seroepidemiological Study. Lancet. 2020 08 22;396(10250):535-544. PubMed PMID: 32645347.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study. AU - Pollán,Marina, AU - Pérez-Gómez,Beatriz, AU - Pastor-Barriuso,Roberto, AU - Oteo,Jesús, AU - Hernán,Miguel A, AU - Pérez-Olmeda,Mayte, AU - Sanmartín,Jose L, AU - Fernández-García,Aurora, AU - Cruz,Israel, AU - Fernández de Larrea,Nerea, AU - Molina,Marta, AU - Rodríguez-Cabrera,Francisco, AU - Martín,Mariano, AU - Merino-Amador,Paloma, AU - León Paniagua,Jose, AU - Muñoz-Montalvo,Juan F, AU - Blanco,Faustino, AU - Yotti,Raquel, AU - ,, Y1 - 2020/07/06/ PY - 2020/05/28/received PY - 2020/06/14/revised PY - 2020/06/17/accepted PY - 2020/7/10/pubmed PY - 2020/9/2/medline PY - 2020/7/10/entrez SP - 535 EP - 544 JF - Lancet (London, England) JO - Lancet VL - 396 IS - 10250 N2 - 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. SN - 1474-547X UR - https://www.unboundmedicine.com/medline/citation/32645347/full_citation L2 - https://linkinghub.elsevier.com/retrieve/pii/S0140-6736(20)31483-5 DB - PRIME DP - Unbound Medicine ER -