Geographical variation in severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) spread requires seroprevalence studies based on local tests, but robust validation is needed. We summarize an ...evaluation of antibody tests used in a serological study of SARS‐CoV‐2 in Saint Petersburg, Russia. We validated three different antibody assays: chemiluminescent microparticle immunoassay (CMIA) Abbott Architect SARS‐CoV‐2 immunoglobulin G (IgG), enzyme linked immunosorbent assay (ELISA) CoronaPass total antibodies test, and ELISA SARS‐CoV‐2‐IgG‐EIA‐BEST. Clinical sensitivity was estimated with the SARS‐CoV‐2 polymerase chain reaction (PCR) test as the gold standard using manufacturer recommended cutoff. Specificity was estimated using prepandemic sera samples. The median time between positive PCR test results and antibody tests was 21 weeks. Measures of concordance were calculated against the microneutralization test (MNA).Sensitivity was equal to 91.1% (95% confidence intervbal CI: 78.8–97.5), 90% (95% CI: 76.4–96.4), and 63.1% (95% CI 50.2–74.7) for ELISA Coronapass, ELISA VectorBest, and CMIA Abbott, respectively. Specificity was equal to 100% for all the tests. Comparison of receiver operating characteristics has shown lower AUC for CMIA Abbott. The cutoff SC/O ratio of 0.28 for CMIA Abbott resulted in a sensitivity of 80% at the same level of specificity. Less than 33% of the participants with positive antibody test results had neutralizing antibodies in titers 1:80 and above. Antibody assays results and MNA correlated moderately. This study encourages the use of local antibody tests and sets the reference for seroprevalence correction. Available tests' sensitivity allows detecting antibodies within the majority of PCR positive individuals. The Abbott assay sensitivity can be improved by incorporating a new cutoff. Manufacturers' test characteristics may introduce bias into the study results.
Highlights
1)
This report is the first diagnostic performance study of antibody assays used in the representative population‐based serological study of SARS‐CoV‐2 in St. Petersburg, Russia.
2)
The sensitivity for two local assays was equal to 91.1% (95%CI: 78.8‐97.5) and 89.1\% (95%CI: 76.4‐96.4), CMIA Abbott's sensitivity was equal to 63.1\% (95%CI 50.2‐74.7)), with 100% specificity for all the tests.
3)
Moving the S/CO ratio from Abbott assays from manufacturers recommended 1.4 to 0.28 improved sensitivity from 63% to 80%, without loss in specificity.
4)
Less than a third of samples positive for binding antibodies were also positive in the virus neutralization test (with 1:80 titer as a threshold) in the population‐based sample.
São Paulo city has been one of the regions most affected by the COVID-19 pandemic in Brazil. Frequent asymptomatic and oligosymptomatic infections and poor access to diagnostic tests make serosurveys ...crucial to monitor the magnitude of the epidemic and to inform public health policies, such as vaccination plans.
To estimate, early in the epidemic, the seroprevalence of antibodies to SARS-CoV-2 in adults living in the six most affected districts in São Paulo city, and to assess potential associated risk factors.
This was a cross-sectional population-based survey of 1,152 households randomly selected from 72 census tracts. During the period May 4–12, 2020, 463 participants completed a questionnaire on sociodemographic characteristics and history of symptoms in the past two weeks, and provided a blood sample. Prevalence of SARS-CoV-2 antibodies was the outcome of interest and was estimated based on results of two immunoassays, Maglumi SARS-CoV-2 chemiluminescence assay Immunoglobulin (Ig) M (IgM) and IgG, and Roche electrochemiluminescence assay total Ig. Serum samples reactive to either assay were considered positive.
Weighted overall seroprevalence was 6% (95%CI 3.9–8.3%). No association was observed between seropositivity and sex, age group or education level. Participants who reported black and brown skin color showed a 2.7 fold higher prevalence than people with white skin (p = 0.007). Among the 30 seropositive individuals, 14 (46.6%) reported no COVID-19 compatible symptoms in the past two weeks.
This study represents the first assessment of SARS-CoV-2 seroprevalence in the city of São Paulo and 6% is the baseline estimate of a series of population-based seroprevalence surveys. Serological screening using sound serological assays is the key tool to monitoring temporal and geographic changes in the spread of the virus through an important epicenter of the COVID-19 pandemic in Brazil. Ultimately, it may inform prevention and control efforts.
•First study in the Republic of Moldova assessing regional progress towards hepatitis B control targets•The study documented the impact of the hepatitis B vaccination programme in the Republic of ...Moldova•The Republic of Moldova drastically reduced the prevalence of hepatitis B in vaccinated cohorts
The WHO European Region set targets for the control of hepatitis B through immunization, including prevalence of hepatitis B surface antigen (HBsAg) at ≤0.5% in vaccinated cohorts. The Republic of Moldova implemented universal hepatitis B vaccination since 1995. We conducted a nationwide representative serosurvey to estimate HBsAg seroprevalence in children born in 2013 to validate hepatitis B control targets.
We used probability-based sampling and a two-stage cluster design. All children born in 2013 and registered in primary healthcare facilities were eligible for participation. We tested blood samples of all participants for hepatitis B core antibody (anti-HBc), using Enzyme-Linked Immunosorbent Assay (ELISA). Anti-HBc-positive samples were tested for HBsAg and HBsAg-positive samples confirmed, using ELISA. We obtained information on hepatitis B vaccination from vaccination cards.
Of 3352 sampled children, 3064 (91%) participated. Most participating children were 7 years old (n = 3030, 99%), 1426 (48%) were girls. The weighted, national seroprevalence estimate was 3.1% (95% confidence interval = 2.1-4.5) for anti-HBc and 0.21% (95% confidence interval = 0.08-0.53) for HBsAg.
The study demonstrated the impact of hepatitis B vaccination and allowed the Republic of Moldova to validate regional hepatitis B control targets. Other countries with high vaccination coverage could use hepatitis B serosurveys and apply for validation. Sustained efforts in the Republic of Moldova will be crucial on the path to hepatitis B elimination.
•An epidemiological model with a stratified immunity level was constructed.•Without imposing a cut-off value for immune response, titer distributions were analysed.•The basic reproduction number was ...greater than the estimate with the cut-off value.
Seroepidemiological surveillance data has been demonstrated to be useful for estimating the cumulative incidence of influenza, and measures the difference between pre- and post-epidemic seropositive fractions. Despite this, such studies relied on a chosen cut-off value for seropositivity. The aim of the present study is to develop a method to analyze distributions of serial cross-sectional seroepidemiological surveillance datasets using an epidemiological model so that the transmission potential can be estimated without imposing a cut-off value.
A mathematical model of influenza transmission with a discrete antibody titer level was constructed. The final size equation for pre- and post-epidemic titer levels was derived. Subsequently, using the estimated distribution of the dilution increase caused by infection and the measurement error distribution, the model parameters were optimized using the maximum likelihood method. A bootstrap-based confidence interval calculation and sensitivity analysis were also performed.
Without imposing a cut-off value, the cumulative incidence was quantified, thereby yielding an estimate of the basic reproduction number. For the purpose of exposition, the proposed method was applied to influenza A/Victoria/3/75(H3N2) data, and serological data between 1975 and 1976 were compared. The estimated reproduction number was greater than that using the cut-off value of the hemagglutination inhibition level with titer level 20 (dilution 1:20) or above to define positives.
The proposed method without a cut-off value offers an unbiased approach to estimating the cumulative incidence along with the reproduction number. If a cut-off value is required, the results imply that titer level 20 or above may better represent a reasonable cut-off value for calculating the incidence, but it could underestimate the basic reproduction number.
Highlights • We examined horse-exposed persons for serological evidence of previous EIV infection. • Seropositive results against A/equine/Ohio/2007 (H3N8) were detected by three assays. • Antibodies ...against wild human H3N2 influenza virus strains were assessed with little evidence of cross-reactivity. • Risk factors included equine veterinary work, smoking and receipt of human influenza vaccine.
Abstract
After the documentation of sporadic cases of Q fever endocarditis, we conducted a serosurvey to assess Coxiella burnetii exposure on Reunion Island. Two hundred forty-one stored frozen human ...sera were analyzed using an immunofluorescence assay. The weighted seroprevalence of Q fever was of 6.81% (95% confidence interval, 4.02%–9.59%). Despite the absence of infection in youths <20 years of age, exposure was not driven by age or by gender. There was a spatial disparity in exposure across the island, with higher prevalence being reported in regions where ruminant farms are present. The seroprevalence pattern suggests that Q fever is endemic on Reunion Island.
Introducción. La toxoplasmosis es una zoonosis de distribución mundial, cuya población vulnerable está constituida por mujeres embarazadas e individuos inmunosuprimidos. Por tal motivo, la mayoría de ...los estudios de seroprevalencia se llevan a cabo en estos grupos de población y no en la población general. Objetivo. Determinar la seroprevalencia de anticuerpos IgG contra Toxoplasma gondii en donantes del banco de sangre de la Clínica Cardiovascular Santa María, Medellín, Colombia. Métodos. Se seleccionó por conveniencia una muestra constituida por 201 donantes sanos del banco de sangre de la Clínica Cardiovascular Santa María. A estos donantes se les aplicó un cuestionario, en el que se les indagó por datos sociodemográficos y la posible exposición a factores de riesgo relacionados con la toxoplasmosis, y se les tomó una muestra de sangre venosa para determinar los niveles séricos de IgG contra T. gondii, mediante una técnica de inmunoensayo por electroquimioluminiscencia, Resultados. El 29,9% de los donantes presentó una serología reactiva para anticuerpos IgG contra el parásito. Un análisis bivariado reveló que el resultado positivo de la prueba serológica se relacionaba con la edad y el nivel de escolaridad (p=0,007 y p=0,025, respectivamente).Introduction: Toxoplasmosis is a zoonosis of world-wide distribution. Pregnant women and immunosuppressed individuals constitute the susceptible population, reason why most of seroprevalence studies of T. gondii usually are made in these populations over those in healthy population. Objective: We sought to determine the prevalence of T. gondii infection in a sample of healthy blood donors from Medellín (Colombia). Materials and methods: Two hundred and one healthy blood donors from Clínica Cardiovascular Santa María (not selected randomly) were examined for toxoplasmosis infection between December 2000 and January 2010. Socio-demographic and behavioral characteristics acting from each participant were also obtained. Samples of venous blood were tested for anti- T. gondii IgG antibodies by using an electroquimioluminiscence assay. Results: Sixty (29.9%) of 201 donors had a reactive serology to IgG parasite antibodies. Bivariate analysis showed that the infection was related with age and schooling level (p=0,007 and p=0.025, respectively).
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