Dynamics of SARS-CoV-2 seroprevalence during the first year of the COVID-19 pandemic in the Northeast region of Brazil.

In this household-based seroepidemiological survey, we analyzed the dynamics of SARS-CoV-2 seroprevalence during the first year of the COVID-19 pandemic in Sergipe State, Northeast Brazil, the poorest region of the country. A total of 16,547 individuals were tested using a rapid IgM-IgG antibody test and fluorescence immunoassay (FIA). Seroprevalence rates were presented according to age, sex, and geographic region. A comparative analysis was performed between the results obtained in July 2020 (peak of the first wave), August - November 2020 (end of the first wave), and February - March 2021 (beginning of the second wave). Seroprevalence rates in the three phases were estimated at 9.3% (95% CI 8.5-10.1), 12.0% (95% CI 11.2-12.9) and 15.4% (95% CI 14.5-16.4). At the end of the first wave, there was a rise in seroprevalence in the countryside (p < 0.001). At the beginning of the second wave, we found an increase in seroprevalence among women (p < 0.001), adults aged 20 to 59 years (p < 0.001), and the elderly (p < 0.001). In this phase, we found an increase in estimates both in metropolitan areas and in the countryside (p < 0.001). This study showed an increase in SARS-CoV-2 seroprevalence over the first year of the pandemic, with approximately one in six people having anti-SARS-CoV-2 antibodies at the beginning of the second wave of COVID-19. Furthermore, our results suggest a rapid spread of COVID-19 from metropolitan areas to the countryside during the first months of the pandemic.

Seroprofiling of antibodies against endemic human coronaviruses and SARS-CoV-2 in an HIV cohort in Lesotho: correlates of antibody response and seropositivity.

BACKGROUND: Serological data on endemic human coronaviruses (HCoVs) and SARS-CoV-2 in southern Africa are scarce. Here, we report on i) endemic HCoV seasonality, ii) SARS-CoV-2 seroprevalence, and iii) predictive factors for SARS-CoV-2 seropositivity and strength of SARS-CoV-2 and HCoV serological response during a 17-month period at the start of the COVID-19 pandemic among adults living with HIV. METHODS: Plasma samples were collected from February 2020 to July 2021 within an outpatient HIV cohort in Lesotho. We used the ABCORA multiplex immunoassay to measure antibody responses to endemic HCoV (OC43, HKU1, NL63, and 229E) and SARS-CoV-2 antigens. RESULTS: Results of 3'173 samples from 1'403 adults were included. Serological responses against endemic HCoVs increased over time and peaked in winter/spring. SARS-CoV-2 seropositivity reached >35% among samples collected in early 2021 and was associated with female sex (p = 0.004), obesity (p < 0.001), working outside the home (p = 0.02), and recent tiredness (p = 0.005) or fever (p = 0.007). Positive correlations were observed between the strength of response to endemic HCoVs and to SARS-CoV-2, and between older age or obesity and the IgG response to SARS-CoV-2. CONCLUSIONS: These results add to our understanding of the impact of biological, clinical, and social/behavioural factors on serological responses to coronaviruses in southern Africa.

Seroprevalence of antibodies against SARS-CoV-2 in the Valencian Community (Spain) as of October 2022.

OBJECTIVE: To estimate the seroprevalence of SARS-CoV-2 antibodies in the Valencian Community (Spain) in October 2022, when BA.5 was the predominant variant. METHOD: Cross-sectional, region-wide, population-based serosurvey study in 88 randomly selected primary care centers of the Valencian Community. RESULTS: Seroprevalence of anti-nucleocapsid (indicative of past infection) and total receptor binding domain (indicative of past infection or vaccination) antibodies was 71.0% (confidence interval [CI]: 67.8-74.2) and 98.4% (CI: 97.5-99.3), respectively. 66.7% (CI: 63.4-70.0) of the population shows hybrid immunity, but only 43.2% in those 80 and over. CONCLUSIONS: The high proportion of hybrid immunity detected is relevant for public health strategies. A second vaccination booster was advisable in the elderly population.

SARS-CoV-2 seroprevalence and associated factors among migrants with a vocation for permanence, Bucaramanga, Colombia / Seroprevalencia de SARS-CoV-2 y factores asociados en migrantes con vocación de permanencia, Bucaramanga, Colombia / Soroprevalência de SARS-CoV-2 e fatores associados em migrantes com vocação de permanência, Bucaramanga, Colômbia

Introducción: Existen pocos reportes que evalúen la seroprevalencia contra SARS-CoV-2 en población migrante en el mundo. Estos estudios ayudan a conocer la exposición al virus en las poblaciones para implementar acciones que reduzcan el impacto de la infección por SARS-CoV-2. Objetivo: Determinar la seroprevalencia contra SARS CoV-2 en migrantes con vocación de permanencia en Bucaramanga, e identificar factores asociados a la infección previa por SARS-CoV-2. Materiales y métodos: Estudio de corte transversal analítico con muestreo consecutivo. Se incluyeron migrantes adultos en Bucaramanga durante febrero/2021. Se realizaron encuestas e inmunoensayos de quimioluminiscencia para IgM e IgG contra SARS-CoV-2 en suero. Se calcularon razones de prevalencia (RP) con regresión log-binomial. Resultados:Se incluyeron 462 participantes. La seroprevalencia de IgM fue 11,7% (IC95% 9,1­14,9), de IgG fue 32,9% (IC95% 28,8­37,3) y de IgM o IgG fue 36,1% (IC95% 31,9-40,6). Exposición a un caso confirmado (RP:1,54; IC95%1,04-2,29) o sospechoso (RP:1,56; IC95%1,13-2,16) de COVID-19, seis o más convivientes (RP:1,52; IC95%1,05-2,20), estancia en Colombia ≥2 años (RP:1,43; IC95%1,11-1,92) y presencia de síntomas (RP:1,62; IC95%1,26 - 2,10) se asociaron con mayor seroprevalencia de IgG. Discusión:En Bucaramanga, la seroprevalencia en migrantes fue similar a la de migrantes en Kuwait, pero menor que en Paris y Singapur. Conclusión: En migrantes con vocación de permanencia la seroprevalencia contra SARS-CoV-2 fue similar a la reportada en residentes de Bucaramanga. El contacto con casos sospechosos/confirmados de COVID-19 y las condiciones de hacinamiento fueron algunos de los factores asociados a la seroprevalencia.

Introduction:There are few reports assessing anti-SARS-CoV-2 seroprevalence in the migrant population in the world. These studies help to understand the exposure of populations to the virus to take actions to reduce the impact of SARS-CoV-2 infection. Objetive: To determine the anti-SARS-CoV-2 seroprevalence in migrants with a vocation for permanence in Bucaramanga and to identify factors associated with previous SARS-CoV-2 infection. Materials and Methods:Analytical cross-sectional study using consecutive sampling, which included adult migrants in Bucaramanga in February 2021. Surveys were conducted, and chemiluminescent immunoassays were performed to detect IgM and IgG antibodies to SARS-CoV-2 in serum samples. Prevalence ratios (PR) were estimated using a log-binomial regression model. Results:The study enrolled 462 participants. IgM seroprevalence was 11.7% (95% CI 9.1­14.9), IgG seroprevalence was 32.9% (95% CI 28.8­37.3), and IgM or IgG seroprevalence was 36.1% (95% CI 31.9­40.6). Contact with a confirmed case of COVID-19 (PR:1.54; 95% CI 1.04-2.29) or suspected case (PR:1.56; 95% CI 1.13­2.16); living with six or more people (PR: 1.52; 95% CI 1.05­2.20); stay in Colombia ≥ 2 years (PR:1.43; 95% CI 1.11­1.92), and presence of symptoms (PR:1.62; 95%CI 1.26­2.10) were some factors associated with higher IgG seroprevalence. Discussion: In Bucaramanga, SARS-CoV-2 seroprevalence among migrants was similar to the seroprevalences of migrants in Kuwait but lower than migrants in Paris and Singapore. Conclusions: The anti-SARS-CoV-2 seroprevalence among migrants with a vocation for permanence was similar to that reported among residents of Bucaramanga. Contact with suspected or confirmed COVID-19 cases and crowded conditions were some of the factors associated with seroprevalence.

Introdução: Existem poucos relatos que avaliam a soroprevalência contra SARS-CoV-2 na população migrante no mundo. Esses estudos ajudam a conhecer a exposição ao vírus nas populações para implementar ações que reduzam o impacto da infecção por SARS-CoV-2. Objetivo: Determinar a soroprevalência contra SARS CoV-2 em migrantes que pretendem permanecer em Bucaramanga e identificar fatores associados à infecção anterior por SARS-CoV-2. Materiais e Métodos: Estudo analítico transversal com amostragem consecutiva. Foram incluídos migrantes adultos em Bucaramanga durante fevereiro/2021. Foram realizados levantamentos e imunoensaios de quimioluminescência para IgM e IgG contra SARS-CoV-2 no soro. As razões de prevalência (RP) foram calculadas com regressão log-binomial. Resultados: foram incluídos 462 participantes. A soroprevalência de IgM foi de 11,7% (IC 95% 9,1-14,9), de IgG foi de 32,9% (IC 95% 28,8-37,3) e de IgM ou IgG foi de 36,1% (IC95% 31,9-40,6). Exposição a um caso confirmado (RP: 1,54; IC 95% 1,04-2,29) ou caso suspeito (RP: 1,56; IC 95% 1,13-2,16) de COVID-19, seis ou mais coabitantes (RP: 1,52; IC 95% 1,05 -2,20), permanência na Colômbia ≥2 anos (RP: 1,43; IC 95% 1,11-1,92) e presença de sintomas (RP: 1,62; IC95%1,26 - 2,10) foram associados a maior soroprevalência de IgG. Discussão: Em Bucaramanga, a soroprevalência em migrantes foi semelhante à de migrantes no Kuwait, mas menor do que em Paris e Cingapura. Conclusão: Em migrantes com vocação de permanência, a soroprevalência contra SARS-CoV-2 foi semelhante à relatada em residentes de Bucaramanga. O contato com casos suspeitos/confirmados de COVID-19 e as condições de superlotação foram alguns dos fatores associados à soroprevalência.

Prevalence and duration of anti-SARS-CoV-2 antibodies in healthcare workers

Introduction. Knowledge of the seroprevalence and duration of antibodies against SARS-CoV-2 was needed in the early phases of the COVID-19 pandemic and is still necessary for policy makers and healthcare professionals. This information allows us to better understand the risk of reinfection in previously infected individuals. Methods. We investigated the prevalence and duration of detectable antibodies against SARS-CoV-2 in sequentially collected samples from 379 healthcare professionals. Results. SARS-CoV-2 seroprevalence at inclusion was 5.3% (95% confidence interval (CI): 3.3-8.0%) and 25% of seropositive participants reverted during follow-up. At the end of follow-up, the calculated probability of having detectable antibodies among former seropositive participants was 72.2% (95% CI: 54.2-96.2%). Conclusion. Antibodies against SARS-CoV-2 were detectable in a subset of infected individuals for a minimum of 39 weeks.

SARS-CoV-2 seroepidemiology in Mongolia, 2020-2021: a longitudinal national study.

Background: The COVID-19 pandemic has global impacts but is relatively understudied in developing countries. Mongolia, a lower-middle-income country, instituted strict control measures in early 2020 and avoided widespread transmission until vaccines became available in February, 2021. Mongolia achieved its 60% vaccination coverage goal by July 2021. We investigated the distribution and determinants of SARS-CoV-2 seroprevalence in Mongolia over 2020 and 2021. Methods: We performed a longitudinal seroepidemiologic study aligned with WHO's Unity Studies protocols. We collected data from a panel of 5000 individuals in four rounds between October 2020 and December 2021. We selected participants through local health centres across Mongolia by age-stratified multi-stage cluster sampling. We tested serum for the presence of total antibodies against SARS-CoV-2 receptor-binding domain, and levels of anti-SARS-CoV-2 spike IgG and neutralising antibodies. We linked participant data with national mortality, COVID-19 case, and vaccination registries. We estimated population seroprevalence and vaccine uptake, as well as unvaccinated population prior-infection prevalence. Findings: At the final round in late 2021, 82% (n = 4088) of participants completed follow-up. Estimated seroprevalence increased from 1.5% (95% CI: 1.2-2.0), to 82.3% (95% CI: 79.5-84.8) between late-2020 and late-2021. At the final round an estimated 62.4% (95% CI: 60.2-64.5) of the population were vaccinated, and of the unvaccinated population 64.5% (95% CI: 59.7-69.0) had been infected. Cumulative case ascertainment in the unvaccinated was 22.8% (95% CI: 19.1%-26.9%) and the overall infection-fatality ratio was 0.100% (95% CI: 0.088-0.124). Health workers had higher odds for being COVID-19 confirmed cases at all rounds. Males (1.72 (95% CI: 1.33-2.22)) and adults aged 20 and above (12.70 (95% CI: 8.14-20.26)) had higher odds for seroconverting by mid-2021. Among the seropositive, 87.1% (95% CI: 82.3%-90.8%) had SARS-CoV-2 neutralising antibodies by late 2021. Interpretation: Our study enabled tracking of SARS-CoV-2 serological markers in the Mongolian population over one year. We found low SARS-CoV-2 seroprevalence in 2020 and early 2021, with seropositivity increasing over a 3-month interval in 2021 due to vaccine roll out and rapid infection of most of the unvaccinated population. Despite high seroprevalence in Mongolia amongst both vaccinated and unvaccinated individuals by end-2021, the SARS-CoV-2 Omicron immune escape variant caused a substantial epidemic. Funding: World Health Organization, WHO UNITY Studies initiative, with funding by the COVID-19 Solidarity Response Fund and the German Federal Ministry of Health (BMG) COVID-19 Research and development. The Ministry of Health, Mongolia partially funded this study.

Seroprevalence of COVID-19 Antibodies and Factors Associated with Seropositivity: A Population-based Study

Background: Currently, COVID-19 is a global public health problem. This study aimed to estimate the seroprevalence of antibodies related to Covid-19 in the general population in southern Iran. Methods: This cross-sectional population-based study of the seroepidemiological type investigated the serological prevalence of COVID-19 from October to December 2020 in Jahrom, Fars province, Iran. A total of 612 participants were selected using multistage cluster random sampling regardless of age or gender. The dataset in the study included the participants' demographic information, the history of exposure to COVID-19 patients, the history of PCR tests, and the history of COVID-19 symptoms in previous months. In addition, this study examined the raw and survey-weight adjusted estimates with Stata version 14. Finally, logistic regression was performed to identify risk factors for serum prevalence. Results: The participants' mean age was 38.88±13.91 and the majority were 30 to 49 years (51.4%), with a female preponderance (58.7%). The estimated adjusted seroprevalence was 32.66 (95%CI: 28.93-36.63), with 207 positive cases for either IgG or IgM. The results of multivariable logistic regression showed that seropositivity in the participants was 4.95 times more likely associated with a history of positive PCR test (OR: 4.95, 95%CI: 2.46-10.90) and 2.14 times in patients with a history of muscle pain in previous months (OR: 2.14, 95%CI: 1.03-4.47). Conclusion: The actual number of patients with COVID-19 is significantly higher than the number of cases confirmed by the disease monitoring system based on PCR tests. Therefore, tracking individuals' contact with confirmed patients using extensive testing and segregation of asymptomatic patients can help control the epidemic. © Journal of Health Sciences and Surveillance System. All rights reserved.

SARS-CoV-2 Seroprevalence among Health-Care Workers in Isfahan, Iran.

Background: Health-care workers (HCWs) are in the frontline for fighting the coronavirus disease 2019 (COVID-19) pandemic and are at higher risk of acquiring the infection. Therefore, the defining immunity status among HCWs helps mitigate the exposure risk. In this study, we investigated the anti-SARS-CoV-2 immunoglobulin G (IgG) and immunoglobulin M (IgM) and also the associated risk factors in the HCWs working in Isfahan University of Medical Sciences COVID-19 referral hospitals. Materials and Methods: In a cross-sectional study, demographics, COVID-19 symptoms during the past 2 weeks, and health-care details were collected from 200 consenting health workers of COVID-center-hospitals of Isfahan University of Medical Sciences from 23 October to 21 December 2020. The recombinant SARS-CoV2 nucleocapsid protein enzyme-linked immunosorbent assay-based IgM, and IgG antibody tests were evaluated. Data were analyzed using Chi-square and independent-t-student tests, and P < 0.05 was considered significant. Results: One hundred and forty-one women and 59 men with a mean age of 36.4 ± 7.77 years participated in the study. IgG Ab and IgM Ab were positive in 77 (38.5%) and 12 (6%) of samples, respectively, and both antibodies were detected in 9 (4.5%). Higher ages, direct contact with the patients with COVID-19, muscle pain, loss of taste and smell, fever, and cough were the factors associated with antibody seropositivity against SARS-CoV2. Conclusion: This study demonstrated that the prevalence of HCWs with antibodies against SARS-CoV-2 is relatively high in Isfahan University referral hospitals. The development of safety protocols and screening and vaccination strategies in the frontline HCWs must be implemented to reduce the burden of infection.

Is there a higher risk of exposure to Coxiella burnetii for pre-clinical veterinary students?

Coxiella burnetii is globally distributed but evidence of zoonotic transmission in the Caribbean region is scarce. The bacterium presence is suspected on the Caribbean island of St. Kitts. The risk of exposure of veterinary students was reported in other regions of the world but is not documented in the Caribbean region. The present study aimed to evaluate the risk of exposure to C. burnetii for pre-clinical veterinary students (mostly coming from the U.S.) attending an island-based veterinary school. A cross-sectional study was conducted to compare incoming and outgoing veterinary students' seroprevalence. Serology was performed using indirect immunofluorescence assay to test Coxiella burnetii Phase I and Phase II immunoglobulins M and G. Background data were gathered using a standardized questionnaire. A parallel study enrolled veterinary school employees in the same university. Of the 98 participants (48 incoming and 50 outgoing students), 41 (41.8%, 95 %CI: 31.9-52.2) were seropositive to C. burnetii. There was no significant difference between the two groups (45.8% for incoming vs. 38.0% for outgoing students) (p = 0.4). No risk factors (demographic, animal handling practices or background) were significantly more reported in the seropositive group. In the employee study, the seroprevalence was high with 8/15 seropositives (53.3%, 95 %CI: 26.6-78.7). Pre-clinical veterinary students do not have a higher risk of exposure to C. burnetii by attending the veterinary school in St. Kitts, but they are highly exposed before arrival on the island (seroprevalence of 45.8%). Most of these participants had experience with animals either through farming or previous veterinary technician employment. This indicates a high exposure in the U.S. young population aiming to become veterinarians. There is an urgent need to increase C. burnetii surveillance in animals and humans to apply relevant prevention and control measures, including recommendations for vaccination of students and professionals at risk.

Characterisation of infection-induced SARS-CoV-2 seroprevalence amongst children and adolescents in North Carolina.

Few prospective studies have documented the seropositivity among those children infected with severe acute respiratory syndrome coronavirus 2. From 2 April 2021 to 24 June 2021, we prospectively enrolled children between the ages of 2 and 17 years at three North Carolina healthcare systems. Participants received at least four at-home serological tests detecting the presence of antibodies against, but not differentiating between, the nucleocapsid or spike antigen. A total of 1,058 participants were enrolled in the study, completing 2,709 tests between 1 May 2021 and 31 October 2021. Using multilevel regression with poststratification techniques and considering our assay sensitivity and sensitivity, we estimated that the seroprevalence of infection-induced antibodies among unvaccinated children and adolescents aged 2-17 years in North Carolina increased from 15.2% (95% credible interval, CrI 9.0-22.0) in May 2021 to 54.1% (95% CrI 46.7-61.1) by October 2021, indicating an average infection-to-reported-case ratio of 5. A rapid rise in seropositivity was most pronounced in those unvaccinated children aged 12-17 years, based on our estimates. This study underlines the utility of serial, serological testing to inform a broader understanding of the regional immune landscape and spread of infection.

National seroepidemiological study of COVID-19 after the initial rollout of vaccines: Before and at the peak of the Omicron-dominant period in Japan.

Background: Based on routine surveillance data, Japan has been affected much less by COVID-19 compared with other countries. To validate this, we aimed to estimate SARS-CoV-2 seroprevalence and examine sociodemographic factors associated with cumulative infection in Japan. Methods: A population-based serial cross-sectional seroepidemiological investigation was conducted in five prefectures in December 2021 (pre-Omicron) and February-March 2022 (Omicron [BA.1/BA.2]-peak). Anti-nucleocapsid and anti-spike antibodies were measured to detect infection-induced and vaccine/infection-induced antibodies, respectively. Logistic regression was used to identify associations between various factors and past infection. Results: Among 16 296 participants (median age: 53 [43-64] years), overall prevalence of infection-induced antibodies was 2.2% (95% CI: 1.9-2.5%) in December 2021 and 3.5% (95% CI: 3.1-3.9%) in February-March 2022. Factors associated with past infection included those residing in urban prefectures (Tokyo: aOR 3.37 [95% CI: 2.31-4.91], Osaka: aOR 3.23 [95% CI: 2.17-4.80]), older age groups (60s: aOR 0.47 [95% CI 0.29-0.74], 70s: aOR 0.41 [95% CI 0.24-0.70]), being vaccinated (twice: aOR 0.41 [95% CI: 0.28-0.61], three times: aOR 0.21 [95% CI: 0.12-0.36]), individuals engaged in occupations such as long-term care workers (aOR: 3.13 [95% CI: 1.47-6.66]), childcare workers (aOR: 3.63 [95% CI: 1.60-8.24]), food service workers (aOR: 3.09 [95% CI: 1.50-6.35]), and history of household contact (aOR: 26.4 [95% CI: 20.0-34.8]) or non-household contact (aOR: 5.21 [95% CI:3.80-7.14]) in February-March 2022. Almost all vaccinated individuals (15 670/15 681) acquired binding antibodies with higher titers among booster dose recipients. Conclusions: Before Omicron, the cumulative burden was >10 times lower in Japan (2.2%) compared with the US (33%), the UK (25%), or global estimates (45%), but most developed antibodies owing to vaccination.

SARS-CoV-2 Seroprevalence Following a Large-Scale Vaccination Campaign in Portugal: Results of the National Serological Survey, September - November 2021.

INTRODUCTION: Following a COVID-19 mass vaccination campaign, it is important to evaluate the population level of SARS-CoV-2 antibodies. The aim of this study was to estimate the seroprevalence rate of SARS-CoV-2 specific antibodies acquired due to infection or vaccination in the Portuguese population. MATERIAL AND METHODS: The National Serological Survey (third wave - ISN3COVID-19) is a cross-sectional nationwide epidemiological study developed on a sample of 4545 Portuguese residents aged one year or older, between the 28th September 2021 and the 19th November 2021. The SARS-CoV-2 anti-nucleoprotein and anti-spike IgG antibody levels were determined in serum samples using Abbott Chemiluminescent Microparticle Immunoassays. Seroprevalence estimates were stratified by age group, sex, administrative region and self-reported chronic conditions. Medians and respective 95% confidence intervals were used to describe the distribution of SARS-CoV-2 specific antibodies in specific population subgroups. RESULTS: The total seroprevalence rate of SARS-CoV-2 was 86.4% (95% CI: 85.2% to 87.6%). A higher seroprevalence rate was estimated for women (88.3%), 50 to 59 years-old (96.5%) and in those with two or more self-reported chronic conditions (90.8%). A higher IgG (anti-Spike) concentration was observed in individuals vaccinated with the booster dose (median = 1 2601.3 AU/mL; 95% CI: 4127.5 to 19 089.1). CONCLUSION: There was a significant increase in SARS-CoV-2 seroprevalence following the mass vaccination campaign in Portugal. It is important to continue to monitor the distribution of specific SARS-COV-2 antibody at the population level to further inform public health policies.

Seroepidemiology of SARS-CoV-2 on a partially vaccinated island in Brazil: Determinants of infection and vaccine response.

Background: A vaccination campaign targeted adults in response to the pandemic in the City of Rio de Janeiro. Objective: We aimed to evaluate the seroprevalence of SARS-CoV-2 antibodies and identify factors associated with seropositivity on vaccinated and unvaccinated residents. Methods: We performed a seroepidemiologic survey in all residents of Paquetá Island, a neighborhood of Rio de Janeiro city, during the COVID-19 vaccine roll-out. Serological tests were performed from June 16 to June 19, 2021, and adjusted seropositivity rates were estimated by age and epidemiological variables. Logistic regression models were used to estimate adjusted ORs for risk factors to SARS-CoV-2 seropositivity in non-vaccinated individuals, and potential determinants of the magnitude of antibody responses in the seropositive population. Results: We included in the study 3,016 residents of Paquetá (83.5% of the island population). The crude seroprevalence of COVID-19 antibodies in our sample was 53.6% (95% CI = 51.0, 56.3). The risk factors for SARS-CoV-2 seropositivity in non-vaccinated individuals were history of confirmed previous COVID-19 infection (OR = 4.74; 95% CI = 3.3, 7.0), being a household contact of a case (OR = 1.93; 95% CI = 1.5, 2.6) and in-person learning (OR = 2.01; 95% CI = 1.4, 3.0). Potential determinants of the magnitude of antibody responses among the seropositive were hybrid immunity, the type of vaccine received, and time since the last vaccine dose. Being vaccinated with Pfizer or AstraZeneca (Beta = 2.2; 95% CI = 1.8, 2.6) determined higher antibody titers than those observed with CoronaVac (Beta = 1.2; 95% CI = 0.9, 1.5). Conclusions: Our study highlights the impact of vaccination on COVID-19 collective immunity even in a highly affected population, showing the difference in antibody titers achieved with different vaccines and how they wane with time, reinforcing how these factors should be considered when estimating effectiveness of a vaccination program at any given time. We also found that hybrid immunity was superior to both infection-induced and vaccine-induced immunity alone, and online learning protected students from COVID-19 exposure.

Prevalence of SARS-CoV-2 infection among oral health care workers worldwide: A meta-analysis.

OBJECTIVES: This systematic review aimed to answer the following question 'What are the worldwide prevalence of SARS-CoV-2 infection and associated factors among oral health-care workers (OHCWs) before vaccination?' METHODS: Seven databases and registers as well as three grey databases were searched for observational studies in the field. Paired reviewers independently screened studies, extracted data and assessed the methodological quality. Overall seroprevalence for SARS-CoV-2 infection was analysed using a random-effect model subgrouped by professional category. Meta-regression was used to explore whether the Human Development Index (HDI) influenced the heterogeneity of results. The associated factors were narratively evaluated, and the certainty of the evidence was assessed using the GRADE approach. RESULTS: Seventeen studies were included (five cohorts and twelve cross-sectional studies), summing 73 935 participants (54 585 dentists and 19 350 dental assistants/technicians) from 14 countries. The overall estimated pooled prevalence of SARS-CoV-2 infection among OHCWs was 9.3% (95% CI, 5.0%-14.7%; I2  = 100%, p < .01), being 9.5% for dentists (95% CI, 5.1%-15.0%; I2  = 100%, p < .01) and 11.6% for dental assistants/technicians (95% CI, 1.6%-27.4%; I2  = 99.0%, p < .01). In the meta-regression, countries with lower HDI showed higher prevalence of SARS-CoV-2 infection (p = .002). Age, comorbidities, gender, ethnicity, occupation, smoking, living in areas of greater deprivation, job role and location/municipalities, income and protective measures in dental settings were associated with positive serological SARS-CoV-2 test, with very low certainty of evidence. CONCLUSIONS: The SARS-CoV-2 virus infected 9.3% of the OHCWs evaluated worldwide before vaccination. OHCWs should be included in policy considerations, continued research, monitoring and surveillance (PROSPERO CRD42021246520).

Rapid SARS-CoV-2 Seroprevalence Survey in Central and Western Divisions of Fiji, 2021.

During November-December 2021, we performed a SARS-CoV-2 seroprevalence survey in Central and Western Divisions of Fiji. A total of 539 participants 8-70 years of age were 95.5% (95% CI 93.4%-97.1%) seropositive, indicating high community levels of immunity. Seroprevalence studies can inform public health responses to emerging SARS-CoV-2 variants.

Variation in SARS-CoV-2 seroprevalence in children in the region of Asturias, Northern Spain.

BACKGROUND: Updated seroprevalence estimates are important to describe the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) landscape and to guide public health decisions. The aims are to describe longitudinal changes in seroprevalence in children in a region in Northern Spain and to analyze factors associated with SARS-CoV-2 seropositivity. METHODS: Prospective multicenter longitudinal study with subjects recruited from July to September 2020. Children (up to 14 years old) were included and followed up until September 2021. Venous blood samples were collected every six months during three testing rounds and were analyzed for SARS-CoV-2 antibodies. The data regarding epidemiological features, contact tracing, symptoms, and virological tests were collected. The evolution of SARS-CoV-2 seroprevalence during the study and the differences between children with positive and negative SARS-CoV-2 antibody tests were analyzed. RESULTS: Two hundred children were recruited (50.5% girls, median age 9.7 years). The overall seroprevalence increased from round 1 [1.5%, 95% confidence interval (CI) 0.3%-4.3%] to round 2 (9.1%, 95% CI 4.6%-12.7%) and round 3 (16.6%, 95% CI 9.5%-19.6%) (P < 0.001). Main changes occurred in children aged zero to four years (P = 0.001) who lived in urban areas (P < 0.001). None of the children who were previously positive became seronegative. Following multivariable analysis, three variables independently associated with SARS-CoV-2 seropositivity were identified: close contact with coronavirus disease 2019 (COVID-19) confirmed or suspected cases [odds ratio (OR) = 3.9, 95% CI 1.2-12.5], previous positive virological test (OR = 17.1, 95% CI 3.7-78.3) and fatigue (OR = 18.1, 95% CI 1.7-193.4). CONCLUSIONS: SARS-CoV-2 seroprevalence in children has remarkably increased during the time of our study. Fatigue was the only COVID-19-compatible symptom that was more frequent in seropositive than in seronegative children.

Hospital-Wide SARS-CoV-2 seroprevalence in health care workers in a Spanish teaching hospital.

INTRODUCTION: Hospital-wide SARS-CoV-2 seroprevalence is rarely explored and can identify areas of unexpected risk. We determined the seroprevalence against SARS-CoV-2 in all health care workers (HCW) at a hospital. METHODS: Cross-sectional study (14-27/04/2020). We determined SARS-CoV-2 IgG by ELISA in all HCW including external workers of a teaching hospital in Madrid. They were classified by professional category, working area, and risk for SARS-CoV-2 exposure. RESULTS: Among 2919 HCW, 2590 (88,7%) were evaluated. The mean age was 43.8 years (SD 11.1), and 73.9% were females. Globally, 818 (31.6%) workers were IgG positive with no differences for age, sex or previous diseases. Of these, 48.5% did not report previous symptoms. Seropositivity was more frequent in high- (33.1%) and medium- (33.8%) than in low-risk areas (25.8%, p=0.007), but not for hospitalization areas attending COVID-19 and non-COVID-19 patients (35.5 vs 38.3% p>0.05). HWC with a previous SARS-CoV2 PCR-positive test were IgG seropositive in 90.8%. By multivariate logistic regression analysis seropositivity was significantly associated with being physicians (OR 2.37, CI95% 1.61-3.49), nurses (OR 1.67, CI95% 1.14-2.46), nurse assistants (OR 1.84, CI95% 1.24-2.73), HCW working at COVID-19 hospitalization areas (OR 1.71, CI95% 1.22-2.40), non-COVID-19 hospitalization areas (OR 1.88, CI95% 1.30-2.73), and at the Emergency Room (OR 1.51, CI95% 1.01-2.27). CONCLUSIONS: Seroprevalence uncovered a high rate of infection previously unnoticed among HCW. Patients not suspected of having COVID-19 as well as asymptomatic HCW may be a relevant source for nosocomial SARS-CoV-2 transmission.

Seroconversion of COVID-19 in Frontline Healthcare Workers in a Tertiary Care Hospital in Oman.

Objectives: This research aimed to study the seroconversion among frontline staff at the highest risk of exposure to SARS-CoV-2 infections, including emergency department, critical care, and COVID-19 isolation wards in all healthcare job categories. Methods: We conducted a prospective cohort study on the incidence of seroconversion among frontline health care workers (HCWs) at the Royal Hospital, Muscat, Oman. Two sera were collected 12 weeks apart to look for seroconversion. We used proportions with 95% confidence interval (CI) for categorical data and mean/median as appropriate for continuous data. Results: Fourteen out of 328 HCWs seroconverted in this study accounting for an incidence rate of 3.6%, excluding four HCWs that were positive at baseline. The median age was 43.5 (range = 28-57). About 75.0% of HCWs were between 31-49 years old, with a seroconversion rate of 4.9% (95% CI: 2.7-8.1). Females accounted for most seroconverted HCWs (14/257) at a rate of 5.4% (95% CI: 3.1-8.8). Omanis seroconverted with a rate of 6.4% (95% CI 2.6-12.8), whereas non-Omanis seroconverted at a rate 4.3% (95% CI: 2.2-7.5). Ninety-two percent (302/328) of the staff lived in the capital area, and a minority lived outside the capital (3/26). Thirteen Muscat citizens seroconverted at a rate of 4.3% (95% CI: 2.4-7.1). Nurses comprised the majority (accounting for about 81%) followed by doctors (19%) at rates of 5.6% (95% CI: 3.2-9.2) and 4.2% (95% CI: 1.07-10.9), respectively. Staff covering COVID-19 isolation wards and intensive care unit comprised over 60% (n = 10) of those who seroconverted with a rate of 5.4% (95% CI: 2.8-9.5) followed by infectious diseases doctors and adult emergency at 19.0% (n = 3) and 12.5% (n = 1), respectively. Approximately 81.3% (n = 13) of HCWs performed aerosol-generating procedures at a seroconversion rate of 4.3% (95% CI: 2.4-7.1). About 50.0% of those who seroconverted had a positive polymerase chain reaction (PCR) before seroconversion, 25.0% had a negative PCR before second serology testing, and 25.0% were not tested with PCR. Approximately 20.0% of seroconverted staff had no reported symptoms compared to 80.0% who reported symptoms such as sore throat (70.0%), fever (50.0%), myalgia (20.0%), and a less frequency (15.0%) runny nose, loss of smell, and headache. Conclusions: Detection of infection among HCWs is important to prevent further transmission, especially asymptomatic carriers. A combined screening strategy of symptoms, serology, and PCR might help detect potential infections and asymptomatic carriage.

Rapid Increase of Community SARS-CoV-2 Seroprevalence during Second Wave of COVID-19, Yaoundé, Cameroon.

We conducted 2 independent population-based SARS-CoV-2 serosurveys in Yaoundé, Cameroon, during January 27-February 6 and April 24-May 19, 2021. Overall age-standardized SARS-CoV-2 IgG seroprevalence increased from 18.6% in the first survey to 51.3% in the second (p<0.001). This finding illustrates high community transmission during the second wave of COVID-19.

SARS-CoV-2 during pregnancy and associated outcomes: Results from an ongoing prospective cohort.

BACKGROUND: The COVID-19 pandemic is an ongoing global health threat, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Questions remain about how SARS-CoV-2 impacts pregnant individuals and their children. OBJECTIVE: To expand our understanding of the effects of SARS-CoV-2 infection during pregnancy on pregnancy outcomes, regardless of symptomatology, by using serological tests to measure IgG antibody levels. METHODS: The Generation C Study is an ongoing prospective cohort study conducted at the Mount Sinai Health System. All pregnant individuals receiving obstetrical care at the Mount Sinai Healthcare System from 20 April 2020 onwards are eligible for participation. For the current analysis, we included participants who had given birth to a liveborn singleton infant on or before 22 September 2020. For each woman, we tested the latest prenatal blood sample available to establish seropositivity using a SARS-CoV-2 serologic enzyme-linked immunosorbent assay. Additionally, RT-PCR testing was performed on a nasopharyngeal swab taken during labour. Pregnancy outcomes of interest (i.e., gestational age at delivery, preterm birth, small for gestational age, Apgar scores, maternal and neonatal intensive care unit admission, and length of neonatal hospital stay) and covariates were extracted from medical records. Excluding individuals who tested RT-PCR positive at delivery, we conducted crude and adjusted regression models to compare antibody positive with antibody negative individuals at delivery. We stratified analyses by race/ethnicity to examine potential effect modification. RESULTS: The SARS-CoV-2 seroprevalence based on IgG measurement was 16.4% (95% confidence interval 13.7, 19.3; n=116). Twelve individuals (1.7%) were SARS-CoV-2 RT-PCR positive at delivery. Seropositive individuals were generally younger, more often Black or Hispanic, and more often had public insurance and higher pre-pregnancy BMI compared with seronegative individuals. None of the examined pregnancy outcomes differed by seropositivity, overall or stratified by race/ethnicity. CONCLUSION: Seropositivity for SARS-CoV-2 without RT-PCR positivity at delivery (suggesting that infection occurred earlier during pregnancy) was not associated with selected adverse maternal or neonatal outcomes among live births in a cohort sample from New York City.