Preventive behavior against SARS-CoV-2 infection in adults according to whether or not they live with children. A combined analysis of the nationwide COSMO-SPAIN and ENE-COVID surveys

Introduction The protection of children is a major driver of behavior among those in charge of their care. We evaluated whether compliance with preventive measures against SARS-CoV-2 infection among adults living with children was different from that of those not living with them, in 2020. Methods We used the COSMO-SPAIN (N = 867) and the nationally representative ENE-COVID (N = 29,926) surveys to estimate prevalence of compliance (95% confidence interval). Logistic model based standardization methods were applied to estimate standardized prevalence differences (SPrD) to the overall distribution of age, sex, education, history of COVID-19, and residence of other >60 yrs in the household. Results We observed that adults living with children more frequently avoided bars (SPrDENE−COVID: 4.2%;95% CI: 2.3–6.1), crowded places (SPrDCOSMO: 8.0%;95% CI: 0.6–15.1) and did not use public transportation (SPrDENE−COVID: 4.9%;95% CI: 3.0–6.7). They were also more worried about work and family conciliation (SPrDCOSMO: 12.2%;95% CI: 4.8–19.5) and about closure of education centers (SPrDCOSMO: 26.5%;95% CI: 19.4–33.6). Discussion In general, adults living with children adopted slightly more frequently social distancing measures.

Preventive behavior against SARS-CoV-2 infection in adults according to whether or not they live with children. A combined analysis of the nationwide COSMO-SPAIN and ENE-COVID surveys.

Introduction: The protection of children is a major driver of behavior among those in charge of their care. We evaluated whether compliance with preventive measures against SARS-CoV-2 infection among adults living with children was different from that of those not living with them, in 2020. Methods: We used the COSMO-SPAIN (N = 867) and the nationally representative ENE-COVID (N = 29,926) surveys to estimate prevalence of compliance (95% confidence interval). Logistic model based standardization methods were applied to estimate standardized prevalence differences (SPrD) to the overall distribution of age, sex, education, history of COVID-19, and residence of other >60 yrs in the household. Results: We observed that adults living with children more frequently avoided bars (SPrDENE-COVID: 4.2%; 95% CI: 2.3-6.1), crowded places (SPrDCOSMO: 8.0%; 95% CI: 0.6-15.1) and did not use public transportation (SPrDENE-COVID: 4.9%; 95% CI: 3.0-6.7). They were also more worried about work and family conciliation (SPrDCOSMO: 12.2%; 95% CI: 4.8-19.5) and about closure of education centers (SPrDCOSMO: 26.5%; 95% CI: 19.4-33.6). Discussion: In general, adults living with children adopted slightly more frequently social distancing measures.

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).

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.

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.

SARS-CoV-2 surveillance strategy in essential workers of the Madrid City Council during the first epidemic wave in Spain, March-July 2020.

OBJECTIVES: To study prevalence of infection in essential workers of Madrid City Council by occupation, related characteristics, use of protective devices, risk perception, and main concerns about COVID-19 during lockdown. METHODS: A total of 30 231 workers were PCR tested for SARS-CoV-2 infection. Information was collected on COVID-19-related symptoms, risk factors, preventive equipment, and risk perception. The crude prevalence was calculated for infection, use of protective devices, perceived risk and main concerns. Additionally, adjusted prevalence and prevalence ratios (PR) were estimated for these variables using logistic regression models with age, gender, occupation, epidemiological week and laboratory as confounding factors. RESULTS: Overall prevalence of infection was 3.2% (95% CI 3.0% to 3.4%), being higher among policemen (4.4%) and bus drivers (4.2%), but lower among emergency healthcare personnel, firefighters, food market workers and burial services (<2%). Lower excess risk was observed in workers reporting occupational contact with COVID-19 cases only (PR=1.42; 95% CI 1.18 to 1.71) compared with household exposure only (PR=2.75; 95% CI 2.32 to 3.25). Infection was more frequent in symptomatic workers (PR=1.28; 95% CI 1.11 to 1.48), although 42% of detected infections were asymptomatic. Use of facial masks (78.7%) and disinfectants (86.3%) was common and associated with lower infection prevalence (PRmasks=0.68; 95% CI 0.58 to 0.79; PRdisinfectants=0.75; 95% CI 0.61 to 0.91). Over 50% of workers felt being at high risk of infection and worried about infecting others, yet only 2% considered quitting their work. CONCLUSIONS: This surveillance system allowed for detecting and isolating SARS-CoV-2 cases among essential workers, identifying characteristics related to infection and use of protective devices, and revealing specific needs for work-safety information and psychological support.

The C-Terminal Half of SARS-CoV-2 Nucleocapsid Protein, Industrially Produced in Plants, Is Valid as Antigen in COVID-19 Serological Tests.

BACKGROUND: The fight against the current coronavirus disease 2019 (COVID-19) pandemic has created a huge demand of biotechnological, pharmaceutical, research and sanitary materials at unprecedented scales. One of the most urgent demands affects the diagnostic tests. The growing need for rapid and accurate laboratory diagnostic tests requires the development of biotechnological processes aimed at producing reagents able to cope with this demand in a scalable, cost-effective manner, with rapid turnaround times. This is particularly applicable to the antigens employed in serological tests. Recombinant protein expression using plants as biofactories is particularly suitable for mass production of protein antigens useful in serological diagnosis, with a neat advantage in economic terms. METHODS: We expressed a large portion of the nucleoprotein (N) derived from SARS-CoV-2 in Nicotiana benthamiana plants. After purification, the recombinant N protein obtained was used to develop an indirect enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to SARS-CoV-2 in human sera. To validate the ELISA, a panel of 416 sera from exposed personnel at essential services in Madrid City Council were tested, and the results compared to those obtained by another ELISA, already validated, used as reference. Furthermore, a subset of samples for which RT-PCR results were available were used to confirm sensitivity and specificity of the test. RESULTS: The performance of the N protein expressed in plants as antigen in serologic test for SARS-CoV-2 antibody detection was shown to be highly satisfactory, with calculated diagnostic sensitivity of 96.41% (95% CI: 93.05-98.44) and diagnostic specificity of 96.37 (95% CI: 93.05-98.44) as compared to the reference ELISA, with a kappa (K) value of 0.928 (95% CI:0.892-0.964). Furthermore, the ELISA developed with plant-derived N antigen detected SARS-CoV-2 antibodies in 84 out of 93 sera from individuals showing RT-PCR positive results (86/93 for the reference ELISA). CONCLUSION: This study demonstrates that the N protein part derived from SARS-CoV-2 expressed in plants performs as a perfectly valid antigen for use in COVID-19 diagnosis. Furthermore, our results support the use of this plant platform for expression of recombinant proteins as reagents for COVID-19 diagnosis. This platform stands out as a convenient and advantageous production system, fit-for-purpose to cope with the current demand of this type of biologicals in a cost-effective manner, making diagnostic kits more affordable.

Composition and Nutritional Quality of the Diet in Spanish Households during the First Wave of the COVID-19 Pandemic.

In Spain, the health crisis caused by the COVID-19 pandemic led to the declaration of a state of alarm in the whole country in 2020; in this context, a nationwide lockdown was implemented, potentially altering the dietary habits of the population. The aims of this study were to describe the diet and its nutritional quality in Spanish households during the first COVID-19 epidemic wave and to compare them with the same period in 2019. Data on monthly foods and beverages household purchases in 2019 and 2020 were obtained from the nationwide Food Consumption Surveys. In April, there was an average increase, compared with 2019, of more than 40% for all food groups, with significant peaks in: alcoholic beverages (75%), appetizers (60%), eggs (59%), sugar and sweets (52%), and vegetables (50%). In March, the greatest peak was for pulses, with a 63% increment. The mean energy value of purchased foods in April was 2801 kcal/person/day, corresponding to an increase of 771 kcal/person/day (+38%), compared to the same month of 2019 (March and May: +520 kcal (+26%), June: +343 kcal (+18%)). Regarding nutrient density, there was a reduction in calcium, iodine, zinc, selenium, riboflavin, vitamins B12, D, A, especially retinol, and an increase in fibre, sodium, folic acid, carotenes and vitamin E. Alcohol content per 1000 kcal increased by more than 20% from April to July. Food purchase patterns in Spanish households changed during lockdown and after it, with no appreciable improvement in the quality of the diet.

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.