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Introduction: The waning of serum antibodies against severe acute respiratory syndrome coronavirus 2 observed in several studies raises questions about long-term immunity. Lower antibody levels are associated with new cases of COVID-19 even postvaccination, leading to the administration of booster doses. Objectives: To evaluate the postvaccination immune humoral response and the relationship between postvaccination seropositivity rates and demographic data among health care workers 6 months after CoronaVac vaccination. Methods: This was a cross-sectional study including health care workers vaccinated with two doses of CoronaVac after 6 months or more. The present study was conducted with the analysis of postvaccination serology test to assess the level of humoral response (anti-receptor binding domain IgG) after vaccination. Results: A total of 325 participants were enrolled, of whom 76% were female, with a median age of 42 years (20-85; interquartile range 31-53). Overall, 18.8% (61) of the participants results were seropositive for anti-receptor binding domain IgG; 81.2% did not have sufficient quantitative titers. The IgG titers obtained from female health care workers did not differ from those obtained from seropositive male health care workers, regardless of age. Conclusions: A group of positive quantitative titers was identified in the serology test for IgG antibodies against severe acute respiratory syndrome coronavirus 2. Further studies are needed to determine the durability of postvaccination antibodies and how serology testing can be used to determine the ideal timing for booster doses of the vaccine.

Introdução: O declínio dos anticorpos séricos contra a síndrome respiratória aguda grave do coronavirus 2 observado em vários estudos levanta questões sobre a imunidade a longo prazo. Níveis mais baixos de anticorpos estão associados a novos casos de covid-19 mesmo após a vacinação, levando à administração de doses de reforço. Objetivos: Avaliar a resposta imunitária humoral após a vacinação e a relação entre as taxas de soropositividade após a vacinação e dados demográficos em trabalhadores da saúde por mais de 6 meses após a imunização com CoronaVac. Métodos: Estudo transversal incluindo profissionais de saúde vacinados com duas doses de CoronaVac após 6 meses ou mais. O estudo foi realizado com a análise do teste sorológico após a vacinação para avaliar os níveis de resposta humoral (anti-domínio de ligação ao receptor IgG) após a vacinação. Resultados: Neste estudo foram incluídos 325 participantes, 76% do sexo feminino e a idade mediana foi de 42 anos (20-85; intervalo interquartil 31-53). No geral, 18,8% (61) dos resultados dos participantes foram soropositivos para IgG anti-domínio de ligação ao receptor; 81,2% não apresentaram títulos quantitativos suficientes. Os títulos de IgG obtidos para os profissionais de saúde do sexo feminino não foram diferentes daqueles obtidos para os participantes do sexo masculino com soropositividade, independentemente da idade. Conclusões: Foi possível identificar um grupo com títulos quantitativos positivos no teste sorológico para anticorpo IgG contra a síndrome respiratória aguda grave do coronavírus 2. Mais investigações são necessárias para determinar a durabilidade dos anticorpos após a vacinação e como os testes sorológicos podem determinar o momento ideal das doses de reforço da vacina.

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Objectives: Evaluate the prevalence of hospital mortality in older adult patients with femoral fracture undergoing surgical treatment during the COVID-19 pandemic period, and to evaluate whether COVID-19 infection, clinical, and orthopedic factors interfered with mortality. Material and Methods: A retrospective study was conducted by reviewing medical records. Patients over 60 years of age with proximal femoral fracture undergoing surgical treatment were included. Overall mortality was calculated, as well as mortality whose primary or secondary cause was COVID-19 infection, to determine if infection influenced patient mortality. Clinical and orthopedic factors that interfered with mortality were evaluated. Categorical variables were compared using the Chi-square test or Fisher's exact test. Both unpaired t-test (parametric variables) and Mann-Whitney test (non-parametric variables) were used. The Kaplan-Meier mortality curve was constructed. Conclusion: The mortality of older adult patients with femoral fracture undergoing surgical treatment during the COVID-19 pandemic was 4.2%. Male sex, older age, and those who underwent blood transfusion had higher mortality rates. COVID-infected patients had ten times more chance of death and died twice as fast as the non-infected population. Level of Evidence II, Retrospective Study.

Objetivos: Avaliar a mortalidade hospitalar de pacientes idosos com fratura de fêmur submetidos ao tratamento cirúrgico durante o período pandêmico de covid-19. Avaliar se a infecção pelo vírus do covid-19 e os fatores clínicos e ortopédicos interferiram na mortalidade. Material e Métodos: Realizou-se um estudo retrospectivo por levantamento de prontuários. Foram incluídos pacientes acima de 60 anos associados a fratura da extremidade proximal do fêmur e que submetidos a tratamento cirúrgico. Calculou-se a mortalidade geral e também aquela cuja causa principal ou secundária foi a infeção pelo covid-19 para determinar se essa influenciou na mortalidade dos pacientes. Foram avaliados se os fatores clínicos e ortopédicos interferiram na mortalidade e variáveis categóricas foram comparadas pelo teste de Qui-quadrado ou exato de Fisher, utilizando tanto o teste t não pareado (variáveis paramétricas) como o teste de Teste Mann-Whitney (variáveis não paramétricas). Por fim, construiu-se a curva de mortalidade de Kaplan-Meier. Conclusão: A taxa de mortalidade de pacientes idosos com fratura de fêmur submetidos ao tratamento cirúrgico durante a pandemia de Covid foi de 4,2%. Pacientes do sexo masculino, idosos e os que foram submetidos à transfusão sanguínea evoluíram com maior mortalidade. Pacientes infectados pelo Covid tiveram dez vezes mais chance de evoluir para óbito e de forma duas vezes mais rápida que a população não infectada. Nível de Evidência II, Estudo Retrospectivo.

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Between 2 and 8.5% of patients who recover from COVID-19 do not develop antibodies, and the durability of IgG antibodies is under scrutiny. Therefore, the presence and persistence of IgM and IgG antibodies were evaluated in a group of patients diagnosed with SARS-CoV-2 from May to August 2020. Out of 2199 suspected COVID-19 cases, 1264 were confirmed for SARS-CoV-2 by rRT-PCR; 328 consented to participate in the study, with 220 participants followed for 9 months, including 124 men (56%) and 96 women (44%). The primary symptoms were headache, dry cough, and fever. IgG antibodies developed in 95% of patients within 4 weeks post-diagnosis, and a second evaluation at 9 months showed that 72.7% still had detectable IgG antibodies. The presence of IgM in one individual (0.45%) suggested the possibility of reinfection.

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Introduction: COVID-19 vaccination aids pandemic limitation. In Argentina, three vaccines are approved, and healthcare workers are priorized (HCWs). The aim was to determine the effectiveness of COVID-19 vaccines, analyzing change in Immunoglobulin G levels and the incidence of new COVID-19 cases up to 12 months after the second dose. Methods: Prospective cohort of HCWs between March 2021- 2022. COVIDAR IgG test was used to measure antibodies. A mixed-effects model was employed to compare the levels of immunoglobulin G at different time points, Kaplan Meier was used to estimate incident COVID-19 cases. Results: 82 participants were included Adverse events were frequent but mild. All participant showed positive antibody at 12 months. Antibodies levels showed an increase one year after 2nd dose. Sinopharm took a long time to yield positive results. More than half of the people had mild COVID-19 disease. Conclusion: COVID-19 vaccines are safe and effective.

Introducción: La vacunación COVID-19 ayuda a limitar la pandemia. En Argentina, se aprobaron tres vacunas y se priorizó a los trabajadores de la salud (TDS). El objetivo fue determinar la efectividad de las vacunas COVID-19, analizando el cambio en los niveles de Inmunoglobulina G y la incidencia de nuevos casos de COVID-19 hasta 12 meses después de la segunda dosis. Métodos: Cohorte prospectiva de TDS entre marzo de 2021 y 2022. Se utilizó la prueba COVIDAR IgG para medir los anticuerpos. Se empleó un modelo de efectos mixtos para comparar los niveles de inmunoglobulina G en diferentes puntos temporales, se utilizó Kaplan Meier para estimar los casos de COVID-19 incidentes. Resultados: se incluyeron 82 participantes. Los eventos adversos fueron frecuentes pero leves. Todos los participantes mostraron anticuerpos positivos a los 12 meses. Los niveles de anticuerpos mostraron un aumento un año después de la segunda dosis. Sinopharm tardó mucho tiempo en arrojar resultados positivos. Más de la mitad de las personas tuvieron una enfermedad leve de COVID-19. Conclusión: Las vacunas COVID-19 son seguras y efectivas.

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ABSTRACT Objectives: Evaluate the prevalence of hospital mortality in older adult patients with femoral fracture undergoing surgical treatment during the COVID-19 pandemic period, and to evaluate whether COVID-19 infection, clinical, and orthopedic factors interfered with mortality. Material and Methods: A retrospective study was conducted by reviewing medical records. Patients over 60 years of age with proximal femoral fracture undergoing surgical treatment were included. Overall mortality was calculated, as well as mortality whose primary or secondary cause was COVID-19 infection, to determine if infection influenced patient mortality. Clinical and orthopedic factors that interfered with mortality were evaluated. Categorical variables were compared using the Chi-square test or Fisher's exact test. Both unpaired t-test (parametric variables) and Mann-Whitney test (non-parametric variables) were used. The Kaplan-Meier mortality curve was constructed. Conclusion: The mortality of older adult patients with femoral fracture undergoing surgical treatment during the COVID-19 pandemic was 4.2%. Male sex, older age, and those who underwent blood transfusion had higher mortality rates. COVID-infected patients had ten times more chance of death and died twice as fast as the non-infected population. Level of Evidence II, Retrospective Study.

RESUMO Objetivos: Avaliar a mortalidade hospitalar de pacientes idosos com fratura de fêmur submetidos ao tratamento cirúrgico durante o período pandêmico de covid-19. Avaliar se a infecção pelo vírus do covid-19 e os fatores clínicos e ortopédicos interferiram na mortalidade. Material e Métodos: Realizou-se um estudo retrospectivo por levantamento de prontuários. Foram incluídos pacientes acima de 60 anos associados a fratura da extremidade proximal do fêmur e que submetidos a tratamento cirúrgico. Calculou-se a mortalidade geral e também aquela cuja causa principal ou secundária foi a infeção pelo covid-19 para determinar se essa influenciou na mortalidade dos pacientes. Foram avaliados se os fatores clínicos e ortopédicos interferiram na mortalidade e variáveis categóricas foram comparadas pelo teste de Qui-quadrado ou exato de Fisher, utilizando tanto o teste t não pareado (variáveis paramétricas) como o teste de Teste Mann-Whitney (variáveis não paramétricas). Por fim, construiu-se a curva de mortalidade de Kaplan-Meier. Conclusão: A taxa de mortalidade de pacientes idosos com fratura de fêmur submetidos ao tratamento cirúrgico durante a pandemia de Covid foi de 4,2%. Pacientes do sexo masculino, idosos e os que foram submetidos à transfusão sanguínea evoluíram com maior mortalidade. Pacientes infectados pelo Covid tiveram dez vezes mais chance de evoluir para óbito e de forma duas vezes mais rápida que a população não infectada. Nível de Evidência II, Estudo Retrospectivo.

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Abstract Objective: To describe study protocol and initial results of research project COVID-Inconfidentes. Method: This paper described the methodological procedures adopted and the prevalence of the SARS-CoV-2 infection in the population. A household survey was conducted between October and December 2020, in two historic cities of Brazil's mining region. Anti-SARS-CoV-2 antibody was detected using the Wondfo® rapid test. The face-to face interview consisted of administration of a questionnaire containing registration data, sociodemographic and economic variables, living habits, general health condition, mental health, sleep habits, and eating and nutrition. Results: We evaluated 1,762 residents, of which 764 (43.4 %) were in Mariana and 998 (56.6 %) in Ouro Preto. For both cities, 51.9 % of the interviewees were female, with a predominance of the age range 35 to 59 years old (47.2 %). The prevalence of the SARS-CoV-2 infection was 5.5 % in both cities, 6.2 % in Ouro Preto, and 4.7 % in Mariana (p-value > 0.05). Conclusion: The study was effective to estimate the seroprevalence of infection by the virus and its findings will enable further analyses of the health conditions of the population related to social isolation and the risk of infection with SARS-CoV-2.

Resumen Describir el protocolo de estudio y los resultados iniciales del proyecto de investigación COVID Inconfidentes. Método: Este artículo describe los procedimientos metodológicos adoptados y la prevalencia de la infección por SARS-CoV-2 en la población. Se realizó una encuesta domiciliaria entre octubre y diciembre de 2020, en dos ciudades históricas de la región minera de Brasil. El anticuerpo anti-SARS-CoV-2 se detectó mediante la prueba rápida Wondfo®. La entrevista cara a cara consistió en la administración de un cuestionario que contenía datos de registro, variables sociodemográficas y económicas, hábitos de vida, estado general de salud, salud mental, hábitos de sueño, alimentación y nutrición. Resultados: Se evaluaron 1.762 habitantes, de los cuales 764 (43,4 %) estaban en Mariana y 998 (56,6 %) en Ouro Preto. Para ambas ciudades, el 51,9 % de los entrevistados eran del sexo femenino, con predominio del rango de edad de 35 a 59 años (47,2 %). La prevalencia de la infección por SARS-CoV-2 fue del 5,5 % en ambos municipios, del 6,2 % en Ouro Preto y del 4,7 % en Mariana (p > 0,05). Conclusión: El estudio fue efectivo para estimar la seroprevalencia de infección por el virus y sus hallazgos permitirán analizar más las condiciones de salud de la población relacionadas con el aislamiento social y el riesgo de infección por SARS-CoV-2.

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[This corrects the article on p. 100 in vol. 12, PMID: 36196438.].

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Vaccines are critical cost-effective tools to control the COVID-19 pandemic. The heterologous prime-boost vaccination has been used by many countries to overcome supply issues, so the effectiveness and safety of this strategy need to be better clarified. This study aims to verify the effect of heterologous prime-boost COVID-19 vaccination on healthcare professionals from Dante Pazzanese Hospital in Brazil. It was performed serological assays of vaccinated individuals after 2-dose of CoronaVac (Sinovac; n = 89) or ChAdOx1 nCoV-19 (Oxford-AstraZeneca; n = 166) followed by a BNT162b2 booster (Pfizer-BioNTech; n = 255). The serum antibodies anti-S (spike), anti-N (nucleocapsid), and anti-RBD (receptor binding domain) were assessed by enzyme-linked immunosorbent assay. The heterologous booster dose induced a 10-fold higher anti-Spike antibody regardless of the 2-dose of a prime vaccine. It was strikingly observed that BNT162b2 enhanced levels of anti-spike antibodies, even in those individuals who did not previously respond to the 2-dose of CoronaVac. In conclusion, the heterologous scheme of vaccination using mRNA as a booster vaccine efficiently enhanced the antibody response against SARS-CoV-2, especially benefiting those elderly who were seronegative with a virus-inactivated vaccine.

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PURPOSE: This study aims to estimate the overall SARS-CoV-2 seroprevalence and evaluate the accuracy of an antibody rapid test compared to a reference serological assay during a COVID-19 outbreak in a prison complex housing over 13,000 prisoners in Brasília. DESIGN/METHODOLOGY/APPROACH: The authors obtained a randomized, stratified representative sample of each prison unit and conducted a repeated serosurvey among prisoners between June and July 2020, using a lateral-flow immunochromatographic assay (LFIA). Samples were also retested using a chemiluminescence enzyme immunoassay (CLIA) to compare SARS-CoV-2 seroprevalence and 21-days incidence, as well as to estimate the overall infection fatality rate (IFR) and determine the diagnostic accuracy of the LFIA test. FINDINGS: This study identified 485 eligible individuals and enrolled 460 participants. Baseline and 21-days follow-up seroprevalence were estimated at 52.0% (95% CI 44.9-59.0) and 56.7% (95% CI 48.2-65.3) with LFIA; and 80.7% (95% CI 74.1-87.3) and 81.1% (95% CI 74.4-87.8) with CLIA, with an overall IFR of 0.02%. There were 78.2% (95% CI 66.7-89.7) symptomatic individuals among the positive cases. Sensitivity and specificity of LFIA were estimated at 43.4% and 83.3% for IgM; 46.5% and 91.5% for IgG; and 59.1% and 77.3% for combined tests. ORIGINALITY/VALUE: The authors found high seroprevalence of anti-SARS-CoV-2 antibodies within the prison complex. The occurrence of asymptomatic infection highlights the importance of periodic mass testing in addition to case-finding of symptomatic individuals; however, the field performance of LFIA tests should be validated. This study recommends that vaccination strategies consider the inclusion of prisoners and prison staff in priority groups.

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Objetivo: Analisar a ocorrência de pacientes cirúrgicos assintomáticos com teste para COVID-19 positivo, delimitar o perfil epidemiológico, identificar o tipo de cirurgia e a especialidade, bem como determinar o tempo de execução do procedimento cirúrgico após testagem positiva. Método: Trata-se de um estudo de coorte retrospectiva, em um hospital de grande porte, filantrópico, de São Paulo, realizado no período de março a setembro de 2020, baseado na análise de dados de prontuário. Resultados: Foram 4.870 procedimentos cirúrgicos, dos quais 3.688 pacientes tiveram coleta de exame PCR. A ocorrência de pacientes cirúrgicos posi-tivos e assintomáticos foi de 1,7%; no perfil epidemiológico, observa-se predominância de sexo masculino, meia-idade, com classificação de risco anestésico ASA II e em procedimentos das especialidades de ortopedia, urologia, ginecologia e gastroenterologia. A execução do teste foi de dois dias pré-procedimento e a presença de pacientes com sintomas em até 14 dias após testagem foi de 0,5%. Conclusão: A ocorrência de pacientes cirúrgicos positivos e assintomáticos foi pequena dentro do quantitativo analisado, os achados deste estudo são similares aos de estudos nacionais e internacionais em relação a especialidade, comorbidades e idade

Objective: To analyze the occurrence of asymptomatic surgical patients with a positive COVID-19 test, delimit the epidemiological profile, iden-tify the type of surgery and specialty, as well as determine the time for performing the surgical procedure after a positive test. Method: This is a retrospective cohort study, in a large, philanthropic hospital in São Paulo, carried out from March to September 2020, based on the analysis of medical records. Results:There were 4,870 surgical procedures, of which 3,688 patients underwent a PCR test. The occurrence of positive and asymptomatic surgical patients was 1.7%; in the epidemiological profile, there is a predominance of males, middle-aged, with ASA II anesthetic risk classification and in procedures of the spe-cialties of orthopedics, urology, gynecology, and gastroenterology. The test was carried out two days before the procedure and the presence of patients with symptoms within 14 days after testing was 0.5%. Conclusion: The occurrence of positive and asymptomatic surgical patients was small within the quantita-tive analyzed, the findings of this study are similar to those of national and international studies in relation to specialty, comorbidities, and age

Objetivo: Analizar la ocurrencia de pacientes quirúrgicos asintomáticos con prueba COVID-19 positiva, delimitar el perfil epidemiológico, iden-tificar el tipo de cirugía y especialidad, así como determinar el tiempo para realizar el procedimiento quirúrgico luego de una prueba positiva. Método:Este es un estudio de cohorte retrospectivo, en un gran hospital filantrópico de São Paulo, realizado de marzo a septiembre de 2020, basado en el análi-sis de registros médicos. Resultados: Se realizaron 4.870 procedimientos quirúrgicos, de los cuales se recolectó examen PCR a 3.688 pacientes. La ocur-rencia de pacientes quirúrgicos positivos y asintomáticos fue de 1,7%; en el perfil epidemiológico predomina el sexo masculino, de mediana edad, con clasificación de riesgo anestésico ASA II y en procedimientos de las especialidades de ortopedia, urología, ginecología y gastroenterología. La prueba se realizó dos días antes del procedimiento y la presencia de pacientes con síntomas dentro de los 14 días posteriores a la prueba fue del 0,5%. Conclusión:La ocurrencia de pacientes quirúrgicos positivos y asintomáticos fue pequeña dentro de lo cuantitativo analizado, los hallazgos de este estudio son simi-lares a los de estudios nacionales e internacionales en relación a especialidad, comorbilidades y edad

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Objective: The aim of this study was to determine current and previous SARS-COV-2 infection, and describe risk factors associated with seropositivity, among HCWs and hospital staff between June and October of 2020. Methodology: Data from the day of enrollment for a prospective cohort study were analyzed to determine point prevalence and seroprevalence of SARS-CoV-2 infection in HCWs and hospital staff of a university hospital in Colombia. Respiratory samples were collected to perform RT-PCR tests, along with blood samples to measure SARS-CoV-2 IgM and IgG antibodies. Data on nosocomial and community risk factors for infection were also collected and analyzed. Findings: 420 HCWs and hospital staff members were included. The seroprevalence at baseline was 23.2%, of which 10.7% had only IgM antibodies, 0.7% had IgG, and 11.7% had IgM and IgG. The prevalence of acute SARS-CoV-2 infection was 1.9%. Being a nurse assistant was significantly associated with seropositivity when compared with all other job duties (PR 2.39, 95% CI 1.27-3.65, p = 0.01). Conclusions: Overall SARS-CoV-2 prevalence was 1.9% and seroprevalence was 23.15%. Nurse assistants, medical doctors or students, and laboratory workers had a higher possibility of being SARS-CoV-2 seropositive.

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Vaccination certainly is the best way to fight against the COVID-19 pandemic. In this study, the seroconversion effectiveness of two vaccines against severe acute respiratory syndrome coronavirus 2 was assessed in healthcare workers: virus-inactivated CoronaVac (CV, n = 303), and adenovirus-vectored Oxford-AstraZeneca (AZ, n = 447). The immunoglobulin G (IgG) antibodies anti-spike glycoprotein and anti-nucleocapsid protein were assessed by enzyme-linked immunosorbent assay at the time before vaccination (T1), before the second dose (T2), and 30 days after the second dose (T3). Of all individuals vaccinated with AZ, 100% (n = 447) exhibited seroconversion, compared to 91% (n = 276) that were given CV vaccine. Among individuals who did not respond to the CV, only three individuals showed a significant increase in the antibody level 4 months later the booster dose. A lower seroconversion rate was observed in elders immunized with the CV vaccine probably due to the natural immune senescence, or peculiarity of this vaccine. The AZ vaccine induced a higher humoral response; however, more common side effects were also observed. Nonvaccinated convalescent individuals revealed a similar rate of anti-spike IgG to individuals that were given two doses of CV vaccine, which suggests that only a one-shot COVID-19 vaccine could produce an effective immune response in convalescents.

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INTRODUCTION: Older adults are at a higher risk of severe illness and death from COVID-19. This vulnerability increases in those who live in long-term care facilities due to overcrowding, greater physical dependence, and contact with health workers. Evidence on the impact of the pandemic on these establishments in lowand middle-income countries has been scant. This study aims to determine the seroprevalence of SARS-CoV-2 in older people residing in long-term care facilities and estimate the impact of infection after the first wave of the pandemic. METHODS: A cross-sectional design with 2099 residents in three regions of Chile was carried out between September and November 2020. Measurement of antibodies was performed with a rapid test. The impact of SARS-CoV-2 infection was estimated with seropositive residents, those who had a history of positive polymerase chain reaction tests, and those who died from COVID-19. Bivariate analysis with the region, sex, age, history of COVID-19, physical dependence, and serological results were performed. In addition, we performed a correlation analysis between the seroprevalence of the centers by the municipality and the rate of confirmed cases. RESULTS: The seroprevalence of SARS-CoV-2 antibodies in the three regions was 14.7% (95% confidence interval: 13.2 to 16.3%), the infection impact was 46.4%, and the fatality rate was 19.6%. A significant correlation was found between the seroprevalence of older adults residing in long-term care facilities and the cumulative incidence by municipalities. CONCLUSIONS: The seroprevalence of older adults residing in long-term care facilities was higher than the general population. The high impact of infection among this population at the end of the first wave of the COVID-19 pandemic is similar to other countries. The centers' environment is directly related to COVID-19 infection. Morbidity and mortality monitoring systems should be implemented promptly to establish prevention and control measures.

INTRODUCCIÓN: Las personas mayores tienen más riesgo de enfermar gravemente y fallecer por COVID-19. Esta vulnerabilidad aumenta en quienes viven en establecimientos de larga estadía, debido a hacinamiento, mayor dependencia física y contacto con los trabajadores. La evidencia sobre el impacto de la pandemia de estos establecimientos en países de medianos y bajos ingresos ha sido escasa. El objetivo es determinar la seroprevalencia de la infección por SARS-CoV-2 en personas mayores que residen en establecimientos de larga estadía. Así como estimar el impacto global de la infección después de la primera ola de la pandemia. MÉTODOS: Diseño transversal con 2099 residentes en tres regiones de Chile, realizado entre septiembre y noviembre 2020. Anticuerpos fueron medidos con test rápido contra SARS-CoV-2. Se estimó el impacto de la infección con los residentes seropositivos, los residentes con antecedentes de reacción en cadena de la polimerasa de transcripción inversa positiva, y residentes que murieron por COVID-19. Análisis bivariado entre el resultado serológico y región, sexo, edad, antecedentes de COVID-19 y dependencia física fueron realizados. Además, realizamos un análisis de correlación entre la seroprevalencia de los centros por municipio y la tasa acumulada de casos confirmados. RESULTADOS: La seroprevalencia de anticuerpos en las tres regiones fue 14,7% (intervalo de confianza del 95%: 13,2 a 16,3%). El impacto real de la infección se estimó en 46,4% y la tasa de letalidad en 19,6%. La seroprevalencia de los residentes de los centros por comuna se correlacionó positiva y significativamente con la frecuencia de la enfermedad a nivel comunal. CONCLUSIONES: Seroprevalencia superior a la de la población general, observándose un alto impacto de la infección por COVID-19 al final de la primera ola de la pandemia. El lugar en el que se encuentran los establecimientos está directamente relacionado con la tasa de seroprevalencia en ellos. Sistemas de vigilancia epidemiológica deben aplicarse con prontitud para establecer medidas de prevención y control.

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RESUMEN Se realizó un estudio transversal en estudiantes de Medicina de una universidad privada de Lima. El objetivo fue describir el nivel de conocimientos y las actitudes sobre la COVID-19, además de su percepción sobre el rol de los medios de comunicación y de las redes sociales. El 32% no sabía que en los primeros cinco días de la enfermedad, las pruebas serológicas son preferibles para diagnosticar la COVID-19, comparadas con las pruebas moleculares; el 73% reportó estar dispuesto a trabajar como voluntario durante la pandemia y el 94% recibió información falsa sobre la COVID-19 en las redes sociales. Este estudio demuestra que la información sobre el uso de pruebas diagnósticas debe ser reforzada y que se debe tomar en cuenta el alto porcentaje de estudiantes dispuestos a ser voluntarios durante la pandemia de la COVID-19.

ABSTRACT A cross-sectional study was carried out on medical students from a private Peruvian university. The aim was to describe knowledge and attitudes towards COVID-19 as well as the student's perception of the role of media outlets and social media. Of the students, 32% did not know that during the first five days of illness, serological tests are preferred for diagnosing COVID-19 over molecular tests; 73% reported being willing to work as a volunteer during the pandemic, and 94% received false information regarding COVID-19 on social media. This study demonstrated that information regarding diagnostic tests should be reinforced and that the high percentage of students willing to volunteer during the COVID-19 pandemic should not be overlooked.

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Abstract Introduction As the Coronavirus Disease 2019 (COVID-19) pandemic unfolds around the world; answers related to the antibody response against the virus are necessary to develop treatment and prophylactic strategies. We attempted to understand part of the immune response of convalescent plasma donation candidates. Method We carried out a cross-sectional, observational, non-intervention study, testing 102 convalescent plasma donation candidates for antibodies against the virus, relating these data to the time interval between symptom onset and sample collection, age, disease severity, and gender. Results In our sample, the individuals who developed a greater antibody response were the ones who had a longer time interval between symptom onset and sample collection, the ones who had been hospitalized and the subjects above 35 years old. Moreover, 17 individuals did not present any reactive antibodies. Conclusion These results are important in that they raise questions about the role of the humoral response against the virus, as some individuals do not develop antibodies to fight it. In addition, they help develop recruitment strategies for convalescent plasma donors, who should be asymptomatic for at least 21 days and are possibly more likely to have reactive antibodies after 35 days without symptoms.

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INTRODUCTION: As the Coronavirus Disease 2019 (COVID-19) pandemic unfolds around the world; answers related to the antibody response against the virus are necessary to develop treatment and prophylactic strategies. We attempted to understand part of the immune response of convalescent plasma donation candidates. METHOD: We carried out a cross-sectional, observational, non-intervention study, testing 102 convalescent plasma donation candidates for antibodies against the virus, relating these data to the time interval between symptom onset and sample collection, age, disease severity, and gender. RESULTS: In our sample, the individuals who developed a greater antibody response were the ones who had a longer time interval between symptom onset and sample collection, the ones who had been hospitalized and the subjects above 35 years old. Moreover, 17 individuals did not present any reactive antibodies. CONCLUSION: These results are important in that they raise questions about the role of the humoral response against the virus, as some individuals do not develop antibodies to fight it. In addition, they help develop recruitment strategies for convalescent plasma donors, who should be asymptomatic for at least 21 days and are possibly more likely to have reactive antibodies after 35 days without symptoms.

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Abstract: This cross-sectional study aimed to determine the seroprevalence of SARS-CoV-2 infection among Brazilian dentists and its associated factors. Stratified random sampling of dentists from 33 administrative regions of the Federal District (Brazil) was performed. The presence of antibodies was verified by the OnSite COVID-19 IgG/IgM Rapid Test. Participants answered a survey about sociodemographic characteristics, exposure to COVID-19, and professional practice. A chi-square test was performed between serostatus and exposure variables. Mann-Whitney tests were carried out for quantitative variables. Odds ratio (OR) and 95% confidence intervals (95%CI) were calculated. A series of binomial logistic regression models was performed. The seroprevalence of SARS-CoV-2 infection among 324 selected dentists was 19.1%. There was a statistically significant association between seropositivity and previous confirmed diagnosis of COVID-19, loss of taste or smell, diagnosis of COVID-19 in a household member, and treatment of a patient with fever. Dentists with a previous confirmed diagnosis of COVID-19 had 29.5 [12.7-68.4] higher odds to exhibit positive serology test results. Dentists with confirmed diagnosis of COVID-19 in a household member had 2.5 [1.1-5.3] times higher odds to exhibit positive serology test results. Professionals with loss of taste or smell in the last 15 days had 5.24 [1.1-24.1] times higher odds to exhibit positive serology test results, and, for those who had treated patients with fever, there were 2.99 [1.03-8.7] times higher odds to exhibit negative serology test results. There was a similar prevalence rate of infection among dentists and in the general population. Nevertheless, this finding applies to the epidemiological situation in 2020, before the development of vaccines and the emergence of SARS-CoV-2 Delta variant.

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Developing countries have reported lower molecular diagnostic testing levels due to a lack of resources. Therefore, antibody tests represent an alternative to detect exposure to SARS-CoV-2 and analyze possible risk factors. We aimed to describe and compare the clinical-epidemiological characteristics and the quality of food intake in Mexican individuals with a positive or negative test to antibodies against SARS-CoV-2. We carried out antibody tests and applied a survey to 1799 individuals; 42% were positive, and diabetes was more prevalent in these cases (p < 0.01). No differences were identified in the blood type nor influenza vaccination between groups. Coughing, respiratory distress, muscle pain, joint pain, and anosmia were the most prevalent symptoms among seropositive cases (p < 0.0001). Food intake quality was similar in both groups, except for the most consumed type of fat (p = 0.006). In conclusion, this study supports the association of diabetes as a principal risk factor for SARS-CoV-2 infection in the Mexican population. The results do not support previous associations between blood group or influenza vaccination as protective factors against SARS-CoV-2 infection. However, frequent consumption of polyunsaturated fats is highlighted as a new possible associated factor with COVID-19, which more studies should corroborate as with all novel findings.

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We performed a retrospective screening of 428 serum samples for anti-SARS-CoV-2  immunoglobulin during a period of low prevalence. Employing two different serological tests yielded discrepant results for 10 samples; highlighting an increased risk of potential  false positive results and the need for further confirmatory testing before publication of data.

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Massive worldwide serological testing for SARS-CoV-2 is needed to determine the extent of virus exposure in a particular region, the ratio of symptomatic to asymptomatic infected persons, and the duration and extent of immunity after infection. To achieve this, the development and production of reliable and cost-effective SARS-CoV-2 antigens is critical. We report the bacterial production of the peptide S-RBDN318-V510, which contains the receptor-binding domain of the SARS-CoV-2 spike protein (region of 193 amino acid residues from asparagine-318 to valine-510) of the SARS-CoV-2 spike protein. We purified this peptide using a straightforward approach involving bacterial lysis, his-tag-mediated affinity chromatography, and imidazole-assisted refolding. The antigen performances of S-RBDN318-V510 and a commercial full-length spike protein were compared in ELISAs. In direct ELISAs, where the antigen was directly bound to the ELISA surface, both antigens discriminated sera from non-exposed and exposed individuals. However, the discriminating resolution was better in ELISAs that used the full-spike antigen than the S-RBDN318-V510. Attachment of the antigens to the ELISA surface using a layer of anti-histidine antibodies gave equivalent resolution for both S-RBDN318-V510 and the full-length spike protein. Results demonstrate that ELISA-functional SARS-CoV-2 antigens can be produced in bacterial cultures, and that S-RBDN318-V510 may represent a cost-effective alternative to the use of structurally more complex antigens in serological COVID-19 testing.