SARS-CoV-2 Infection During the First and Second Pandemic Waves in Spain: the ENE-COVID Study.

Objectives. To describe participant characteristics associated with severe acute respiratory syndrome coronavirus 2 infection in Spain's first 2 COVID-19 waves per the Spanish National Seroepidemiological Survey of SARS-CoV-2 Infection (ENE-COVID). Methods. A representative cohort of the noninstitutionalized Spanish population, selected through stratified 2-stage sampling, answered a questionnaire and received point-of-care testing April to June 2020 (first wave: n = 68 287); previously seronegative participants repeated the questionnaire and test November 2020 (second wave: n = 44 451). We estimated seropositivity by wave and participant characteristics, accounting for sampling weights, nonresponse, and design effects. Results. We found that 6.0% (95% confidence interval [CI] = 5.7%, 6.4%) of Spain's population was infected by June and 3.8% (95% CI = 3.5%, 4.1%) more by November 2020. Both genders were equally affected. Seroprevalence decreased with age in adults 20 years and older in the second wave; socioeconomic differences increased. Health care workers were affected at 11.1% (95% CI = 9.0%, 13.6%) and 6.1% (95% CI = 4.4%, 8.5%) in the first and second waves, respectively. Living with an infected person increased infection risk to 22.1% (95% CI = 18.9%, 25.6%) in the first and 35.0% (95% CI = 30.8%, 39.4%) in the second wave. Conclusions. ENE-COVID characterized the first 2 pandemic waves, when information from surveillance systems was incomplete. (Am J Public Health. 2023;113(5):533-544. https://doi.org/10.2105/AJPH.2023.307233).

Design and Implementation of a Nationwide Population-Based Longitudinal Survey of SARS-CoV-2 Infection in Spain: The ENE-COVID Study.

Data System. The Spanish National Seroepidemiological Survey of SARS-CoV-2 (or ENE-COVID; SARS-CoV-2 [severe acute respiratory syndrome coronavirus 2] is the causative agent of COVID-19) was funded by the Spanish Ministry of Health, the Instituto de Salud Carlos III, and the Spanish National Health System. Data Collection/Processing. A stratified 2-stage probability sampling was used to select a representative cohort of the noninstitutionalized population of Spain. ENE-COVID collected longitudinal data from epidemiological questionnaires and 2 SARS-CoV-2 IgG antibody tests. From April 27 to June 22, 2020, 68 287 participants (77.0% of contacted persons) received a point-of-care test and 61 095 (68.9%) also underwent a laboratory immunoassay. A second follow-up phase was conducted between November 16 and 30, 2020. Data Analysis/Dissemination. Analyses use weights to adjust for oversampling and nonresponse and account for design effects of stratification and clustering. ENE-COVID data for research purposes will be available upon request from the official study Web page. Public Health Implications. ENE-COVID, a nationwide population-based study, allowed monitoring seroprevalence of antibodies against SARS-CoV-2 at the national and regional levels, providing accurate figures by gender, age (from babies to nonagenarians), and selected risk factors; characterizing symptomatic and asymptomatic infections; and estimating the infection fatality risk during the first pandemic wave. (Am J Public Health. 2023;113(5):525-532. https://doi.org/10.2105/AJPH.2022.307167).

Evolution of antibodies against SARS-CoV-2 over seven months: Experience of the nationwide seroprevalence ENE-COVID study in Spain.

BACKGROUND: The main aims of this study were to analyze trends of SARS-CoV-2 anti-nucleocapsid IgG throughout the four rounds of the seroepidemiologic study ENE-COVID, and compare the fourth-round results of two immunoassays detecting anti-nucleocapsid and anti-RBD IgG. METHODS: ENE-COVID was developed in 2020 (two phases). Phase one included three rounds carried out in April 27-May 11, May 18-June 1, and June 8-June 22. Phase two included a fourth round in the same cohort (November 16-29). A chemiluminescent microparticle immunoassay was offered to participants in the first three rounds (Abbott; anti-nucleocapsid IgG). In the fourth round, we offered this test and a chemiluminescence immunoassay (Beckman; anti-RBD IgG) to i) a randomly selected sub-cohort, ii) participants who were IgG-positive in any of the three first rounds; and iii) participants who were IgG-positive in the fourth round by point-of-care immunochromatography. RESULTS: 10,153 individuals (82.2% of people invited) participated in the fourth round. Of them, 2595 (35.1% of participants with results in the four rounds) were positive for anti-nucleocapsid IgG in at least one round. Anti-nucleocapsid IgG became undetectable in 43.3% of participants with positive first-round results. In fourth round, anti-nucleocapsid and anti-RBD IgG were detected in 5.5% (321/5827) and 5.4% (315/5827) participants of the randomly selected sub-cohort, and in 26.6% (867/3261) and 25.9% (846/3261) participants with at least one previous positive result, respectively. CONCLUSIONS: The IgG response is heterogeneous and conditioned by infection severity. A proportion of SARS-CoV-2 infected population may have negative serologic results in the post-infection months.

ENE-COVID nationwide serosurvey served to characterize asymptomatic infections and to develop a symptom-based risk score to predict COVID-19.

OBJECTIVES: To characterize asymptomatic SARS-CoV-2 infections and develop a symptom-based risk score useful in primary healthcare. STUDY DESIGN AND SETTING: Sixty-one thousand ninty-two community-dwelling participants in a nationwide population-based serosurvey completed a questionnaire on COVID-19 symptoms and received an immunoassay for SARS-CoV-2 IgG antibodies between April 27 and June 22, 2020. Standardized prevalence ratios for asymptomatic infection were estimated across participant characteristics. We constructed a symptom-based risk score and evaluated its ability to predict SARS-CoV-2 infection. RESULTS: Of all, 28.7% of infections were asymptomatic (95% CI 26.1-31.4%). Standardized asymptomatic prevalence ratios were 1.19 (1.02-1.40) for men vs. women, 1.82 (1.33-2.50) and 1.45 (0.96-2.18) for individuals <20 and ≥80 years vs. those aged 40-59, 1.27 (1.03-1.55) for smokers vs. nonsmokers, and 1.91 (1.59-2.29) for individuals without vs. with case contact. In symptomatic population, a symptom-based score (weights: severe tiredness = 1; absence of sore throat = 1; fever = 2; anosmia/ageusia = 5) reached standardized seroprevalence ratio of 8.71 (7.37-10.3), discrimination index of 0.79 (0.77-0.81), and sensitivity and specificity of 71.4% (68.1-74.4%) and 74.2% (73.1-75.2%) for a score ≥3. CONCLUSION: The presence of anosmia/ageusia, fever with severe tiredness, or fever without sore throat should serve to suspect COVID-19 in areas with active viral circulation. The proportion of asymptomatics in children and adolescents challenges infection control.

Infection fatality risk for SARS-CoV-2 in community dwelling population of Spain: nationwide seroepidemiological study.

OBJECTIVE: To estimate the infection fatality risk for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), based on deaths with confirmed coronavirus disease 2019 (covid-19) and excess deaths from all causes. DESIGN: Nationwide seroepidemiological study. SETTING: First wave of covid-19 pandemic in Spain. PARTICIPANTS: Community dwelling individuals of all ages. MAIN OUTCOME MEASURES: The main outcome measure was overall, and age and sex specific, infection fatality risk for SARS-CoV-2 (the number of covid-19 deaths and excess deaths divided by the estimated number of SARS-CoV-2 infections) in the community dwelling Spanish population. Deaths with laboratory confirmed covid-19 were obtained from the National Epidemiological Surveillance Network (RENAVE) and excess all cause deaths from the Monitoring Mortality System (MoMo), up to 15 July 2020. SARS-CoV-2 infections in Spain were derived from the estimated seroprevalence by a chemiluminescent microparticle immunoassay for IgG antibodies in 61 098 participants in the ENE-COVID nationwide seroepidemiological survey between 27 April and 22 June 2020. RESULTS: The overall infection fatality risk was 0.8% (19 228 of 2.3 million infected individuals, 95% confidence interval 0.8% to 0.9%) for confirmed covid-19 deaths and 1.1% (24 778 of 2.3 million infected individuals, 1.0% to 1.2%) for excess deaths. The infection fatality risk was 1.1% (95% confidence interval 1.0% to 1.2%) to 1.4% (1.3% to 1.5%) in men and 0.6% (0.5% to 0.6%) to 0.8% (0.7% to 0.8%) in women. The infection fatality risk increased sharply after age 50, ranging from 11.6% (8.1% to 16.5%) to 16.4% (11.4% to 23.2%) in men aged 80 or more and from 4.6% (3.4% to 6.3%) to 6.5% (4.7% to 8.8%) in women aged 80 or more. CONCLUSION: The increase in SARS-CoV-2 infection fatality risk after age 50 appeared to be more noticeable in men than in women. Based on the results of this study, fatality from covid-19 was greater than that reported for other common respiratory diseases, such as seasonal influenza.

Prevalence of SARS-CoV-2 in Spain (ENE-COVID): a nationwide, population-based seroepidemiological study.

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.

[Adherence and effectiveness of the treatment of latent tuberculosis infection with isoniazid for 9 months in a cohort of 755 patients]. / Cumplimiento y efectividad del tratamiento de la infección tuberculosa con isoniazida durante 9 meses en una cohorte de 755 pacientes.

BACKGROUND AND OBJECTIVE: The effectiveness of the treatment of latent tuberculosis infection depends on its efficacy, the adherence to treatment and patient's risk of tuberculosis. The objective of this study was to evaluate the adherence to treatment with daily isoniazid for 9 months, its effectiviness and equivalent adherence with daily isoniazid for 6 months so that treatment can be as effective as with daily isoniazid for 9 months. PATIENTS AND METHOD: Cohort of 755 contacts of patients with lung confirmed tuberculosis with latent tuberculosis infection treated from 1986 to 2004, classified according to risk of tuberculosis disease into converters (high risk), frequent and non-frequent contacts. Adherence's rate for daily isoniazid for 9 months is evaluated according to percentage of treatment completion and effectiveness achieved is the number necessary to treat for preventing one tuberculosis case. Efficacy (reduction of morbidity) with isoniazid for 9 months: 93%, and with isoniazid for 6 months: 69%. RESULTS: Adherence's rate: 53/59 (89.9%; 95% confidence interval [CI], 82.1-97.5%) in converters; 305/380 (80.3%; 95% CI, 76.3-84.3%) in frequent contacts; and 205/211 (64.9%; 95% CI, 59.6-70.2%) in non-frequent contacts. The number necessary to treat with isoniazid for 9 months was 9 for converters, 16 for frequent contacts, and 79 for non-frequent contacts. Equivalent adherence for daily isoniazid for 6 months was 121% for converters, 108% for frequent contacts and 87.5% for non-frequent contacts. CONCLUSIONS: For latent tuberculosis infection, a 9-month-isoniazid treatment has the highest effectiveness in the converters and frequent contacts. Such high effectiveness is impossible to achieve with a daily 6-month-isoniazid regimen.

Cumplimiento y efectividad del tratamiento de la infección tuberculosa con isoniazida durante 9 meses en una cohorte de 755 pacientes / Adherence and effectiveness of the treatment of latent tuberculosis infection with isoniazid for 9 months in a cohort of 755 patients

Fundamento y objetivo: La efectividad del tratamiento de la infección tuberculosa depende de su eficacia, la adherencia al tratamiento y el riesgo de enfermar. El objetivo del estudio ha sido evaluar la adherencia al tratamiento con isoniazida durante 9 meses, su efectividad y la adherencia equivalente para conseguir idéntica efectividad a la pauta de isoniazida durante 6 meses. Pacientes y método: Se incluyó en el estudio a contactos de pacientes con tuberculosis pulmonar a quienes se había diagnosticado de infección tuberculosa, clasificados de mayor a menor riesgo de desarrollar la enfermedad (conversores, contactos frecuentes y no frecuentes), y que entre 1986 y 2004 recibieron tratamiento con isoniazida durante 9 meses. Se determinaron la tasa de adherencia, es decir, el porcentaje que completó el tratamiento, y la efectividad como el número de pacientes que es necesario tratar para prevenir que uno desarrolle la enfermedad. La eficacia del tratamiento con isoniazida durante 9 meses es del 93% de reducción de la morbilidad, y la del tratamiento durante 6 meses, del 69%. Resultados: Se estudió a 755 contactos: 59 conversores, 380 contactos frecuentes y 316 contactos no frecuentes. En los primeros la tasa de adherencia fue del 89,9% (intervalo de confianza [IC] del 95%, 82,1-95,7%); en los segundos, del 80,3% (IC del 95%, 76,3-84,3%), y en los terceros, del 64,9% (IC del 95%, 59,6-70,2%). Con isoniazida durante 9 meses, el número de pacientes que era preciso tratar para prevenir que uno desarrollara la enfermedad fue de 9 en conversores, de 16 en contactos frecuentes y de 79 en contactos no frecuentes. Para la misma efectividad, la tasa de adherencia equivalente con isoniazida durante 6 meses sería del 121% en conversores, del 108% en contactos frecuentes y del 87,5% en contactos no frecuentes. Conclusiones: La mayor efectividad del tratamiento de la infección tuberculosa en conversores y contactos frecuentes se ha conseguido con una pauta de isoniazida durante 9 meses, efectividad no alcanzable con la pauta de 6 meses

Background and objective: The effectiveness of the treatment of latent tuberculosis infection depends on its efficacy, the adherence to treatment and patient's risk of tuberculosis. The objective of this study was to evaluate the adherence to treatment with daily isoniazid for 9 months, its effectiviness and equivalent adherence with daily isoniazid for 6 months so that treatment can be as effective as with daily isoniazid for 9 months. Patients and method: Cohort of 755 contacts of patients with lung confirmed tuberculosis with latent tuberculosis infection treated from 1986 to 2004, classified according to risk of tuberculosis disease into converters (high risk), frequent and non-frequent contacts. Adherence's rate for daily isoniazid for 9 months is evaluated according to percentage of treatment completion and effectiveness achieved is the number necessary to treat for preventing one tuberculosis case. Efficacy (reduction of morbidity) with isoniazid for 9 months: 93%, and with isoniazid for 6 months: 69%. Results: Adherence's rate: 53/59 (89.9%; 95% confidence interval [CI], 82.1-97.5%) in converters; 305/380 (80.3%; 95% CI, 76.3-84.3%) in frequent contacts; and 205/211 (64.9%; 95% CI, 59.6-70.2%) in non-frequent contacts. The number necessary to treat with isoniazid for 9 months was 9 for converters, 16 for frequent contacts, and 79 for non-frequent contacts. Equivalent adherence for daily isoniazid for 6 months was 121% for converters, 108% for frequent contacts and 87.5% for non-frequent contacts. Conclusions: For latent tuberculosis infection, a 9-month-isoniazid treatment has the highest effectiveness in the converters and frequent contacts. Such high effectiveness is impossible to achieve with a daily 6-month-isoniazid regimen