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Serosurveys are a widely used tool to estimate the cumulative incidence—the fraction of a population that has been infected by a given pathogen. These surveys rely on serological assays that measure the level of pathogen-specific antibodies. Because antibody levels are waning, the fraction of previously infected individuals that have seroreverted increases with time past infection. To avoid underestimating the true cumulative incidence, it is therefore essential to correct for waning antibody levels. We present an empirically supported approach for seroreversion correction in cumulative incidence estimation when sequential serosurveys are conducted in the context of a newly emerging infectious disease. The correction is based on the observed dynamics of antibody titers in seropositive cases and validated using several in silico test scenarios. Furthermore, through this approach we revise a previous cumulative incidence estimate relying on the assumption of an exponentially declining probability of seroreversion over time, of severe acute respiratory syndrome coronavirus 2, of 76% in Manaus, Brazil, by October 2020 to 47.6% (95% confidence region: 43.5–53.5). This estimate has implications, for example, for the proximity to herd immunity in Manaus in late 2020. [ABSTRACT FROM AUTHOR]

Lyme borreliosis is a public health concern in India. The prevalence of the disease is still undetermined with major entomological and epidemiological gaps. The present study was conducted to determine the seropositivity of Borrelia burgdorferi in Sikkim and Arunachal Pradesh, India. A cross-sectional serosurvey was conducted in Sikkim and Arunachal Pradesh. Data collection tools were developed and standardized for the collection of clinico-socio-demographic data. Sample size for each site was calculated using the formula for the estimation of a single proportion. Qualitative detection of IgG antibodies in serum samples was done using NovaLisa™ Lyme Borrelia IgG ELISA kit. A total of 793 participants were enrolled, 484 (61%) from Arunachal Pradesh and 309 (39%) from Sikkim. Out of 793 participants, 21 (2.7%), 22 (2.8%), 6 (0.8%), 29 (3.7%), 44 (5.5%), and 16 (2.1%) gave history of tick bite, rash, erythema migrans , migratory muscle pain, migratory joint pain, and numbness, respectively, in the past one year. The adjusted seroprevalence (for sensitivity and specificity of kit) for the study is 3.7 (2.4–5.2). No signs or symptoms were found to be associated with IgG ELISA positivity. The state-wise distribution of seropositivity for Arunachal Pradesh and Sikkim was 4.1 (95% CI: 2.5–6.3) and 2.3 (95% CI: 0.9–4.6), respectively. This study establishes the state of Sikkim as a new endemic area in India of Lyme disease besides its already reported endemicity in Arunachal Pradesh. No association was conclusively established between symptoms of Lyme and IgG seropositivity emphasizing the need for detailed history taking and clinical suspicion in endemic areas. [ABSTRACT FROM AUTHOR]

Serological assays used to estimate the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) often rely on manufacturers' cutoffs established on the basis of severe cases. We conducted a household-based serosurvey of 4,677 individuals in Chennai, India, from January to May 2021. Samples were tested for SARS-CoV-2 immunoglobulin G (IgG) antibodies to the spike (S) and nucleocapsid (N) proteins. We calculated seroprevalence, defining seropositivity using manufacturer cutoffs and using a mixture model based on measured IgG level. Using manufacturer cutoffs, there was a 5-fold difference in seroprevalence estimated by each assay. This difference was largely reconciled using the mixture model, with estimated anti-S and anti-N IgG seroprevalence of 64.9% (95% credible interval (CrI): 63.8, 66.0) and 51.5% (95% CrI: 50.2, 52.9), respectively. Age and socioeconomic factors showed inconsistent relationships with anti-S and anti-N IgG seropositivity using manufacturer cutoffs. In the mixture model, age was not associated with seropositivity, and improved household ventilation was associated with lower seropositivity odds. With global vaccine scale-up, the utility of the more stable anti-S IgG assay may be limited due to the inclusion of the S protein in several vaccines. Estimates of SARS-CoV-2 seroprevalence using alternative targets must consider heterogeneity in seroresponse to ensure that seroprevalence is not underestimated and correlates are not misinterpreted. [ABSTRACT FROM AUTHOR]

The introduction of anti-poliomyelitis vaccines has driven progress toward the global eradication of wild polioviruses, a millennium goal of the World Health Organization. With the vaccination campaigns carried out since 1964, in 2002 Italy was certified polio-free, considering that no cases had been recorded since 1983. Nevertheless, it is crucial to guarantee high level of immunization coverage also in low-endemicity countries, considering that sporadic polio cases can be recorded. To evaluate the presence of susceptible subjects in the population, seroepidemiological studies are key actions. We conducted a systematic review of the relevant literature to evaluate the prevalence of anti-PV neutralizing antibodies in Italian population. Seven studies, selected among scientific articles available in MEDLINE/PubMed, ISI Web of Knowledge and Scopus and published from January 1, 2012, to November 15, 2022, were included. The pooled prevalence of subjects without PV1 neutralizing antibodies was 6.4% (95%CI = 0.5–16.9), for PV2 it was 5.3% (95%CI = 0.4–14.2), and for PV3 it was 13.0% (95%CI = 4.0–25.7; I2 = 98.5%). Levels of neutralizing antibodies appears to decrease with increasing age; this decline is a proxy for the real risk factor, which is the time since the last vaccine dose. Public health institutions must be aware of the risk of reintroduction of wild PV in polio-free countries and therefore they must keep high level of immunization in population and reinforce the active surveillance systems. [ABSTRACT FROM AUTHOR]

Objectives: After South Africa's second wave of COVID-19, this study estimated the SARS-CoV-2 seroprevalence among pregnant women in inner-city Johannesburg, South Africa. Methods: In this cross-sectional survey, 500 pregnant women who were non-COVID-19-vaccinated (aged ≥12 years) were enrolled, and demographic and clinical data were collected. Serum samples were tested using the Wantai SARS-CoV-2 spike antibody enzyme-linked immunosorbent assay and Roche Elecsys® anti-SARS-CoV-2 nucleocapsid antibody assays. Seropositivity was defined as SARS-CoV-2 antibodies on either (primary) or both (secondary) assays. Univariate Poisson regression assessed risk factors associated with seropositivity. Results: The median age was 27.4 years, and HIV prevalence was 26.7%. SARS-CoV-2 seroprevalence was 64.0% (95% confidence interval [CI]: 59.6-68.2%) on the primary and 54% (95% CI: 49.5-58.4%) on the secondary measure. Most (96.6%) women who were SARS-CoV-2-seropositive reported no symptoms. On the Roche assay, we detected lower seroprevalence among women living with HIV than women without HIV (48.9% vs 61.7%, P-value = 0.018), and especially low levels among women living with HIV with a clusters of differentiation 4

Abstract Background Lot Quality Assurance Sampling (LQAS), a tool used for monitoring health indicators in low resource settings resulting in “high” or “low” classifications, assumes that determination of the trait of interest is perfect. This is often not true for diagnostic tests, with imperfect sensitivity and specificity. Here, we develop Lot Quality Assurance Sampling for Imperfect Tests (LQAS-IMP) to address this issue and apply it to a COVID-19 serosurveillance study design in Haiti. Methods We first derive a modified procedure, LQAS-IMP, that accounts for the sensitivity and specificity of a diagnostic test to yield correct classification errors. We then apply the novel LQAS-IMP to design an LQAS system to classify prevalence of SARS-CoV-2 antibodies among healthcare workers at eleven Zanmia Lasante health facilities in Haiti. Finally, we show the performance of the LQAS-IMP procedure in a simulation study. Results We found that when an imperfect diagnostic test is used, the classification errors in the standard LQAS procedure are larger than specified. In the modified LQAS-IMP procedure, classification errors are consistent with the specified maximum classification error. We then utilized the LQAS-IMP procedure to define valid systems for sampling at eleven hospitals in Haiti. Conclusion The LQAS-IMP procedure accounts for imperfect sensitivity and specificity in system design; if the accuracy of a test is known, the use of LQAS-IMP extends LQAS to applications for indicators that are based on laboratory tests, such as SARS-CoV-2 antibodies.

Abstract The rapid spread of SARS-CoV-2 is largely driven by pre-symptomatic or mildly symptomatic individuals transmitting the virus. Serological tests to identify antibodies against SARS-CoV-2 are important tools to characterize subclinical infection exposure. During the summer of 2020, a mail-based serological survey with self-collected dried blood spot (DBS) samples was implemented among university affiliates and their household members in Massachusetts, USA. Described are challenges faced and novel procedures used during the implementation of this study to assess the prevalence of SARS-CoV-2 antibodies amid the pandemic. Important challenges included user-friendly remote and contact-minimized participant recruitment, limited availability of some commodities and laboratory capacity, a potentially biased sample population, and policy changes impacting the distribution of clinical results to study participants. Methods and lessons learned to surmount these challenges are presented to inform design and implementation of similar sero-studies. This study design highlights the feasibility and acceptability of self-collected bio-samples and has broad applicability for other serological surveys for a range of pathogens. Key lessons relate to DBS sampling, supply requirements, the logistics of packing and shipping packages, data linkages to enrolled household members, and the utility of having an on-call nurse available for participant concerns during sample collection. Future research might consider additional recruitment techniques such as conducting studies during academic semesters when recruiting in a university setting, partnerships with supply and shipping specialists, and using a stratified sampling approach to minimize potential biases in recruitment.

• A SARS-CoV-2 seroprevalence study was conducted after the second wave of COVID infections. • The study included pregnant women in two urban antenatal clinics in inner-city Johannesburg. • A total of 64% of pregnant women were SARS-CoV-2 seropositive; most (96.6%) were asymptomatic. • No association between HIV status and SARS-CoV-2 seropositivity was found. • Only 60% of pregnant women reported being willing to vaccinate. After South Africa's second wave of COVID-19, this study estimated the SARS-CoV-2 seroprevalence among pregnant women in inner-city Johannesburg, South Africa. In this cross-sectional survey, 500 pregnant women who were non-COVID-19-vaccinated (aged ≥12 years) were enrolled, and demographic and clinical data were collected. Serum samples were tested using the Wantai SARS-CoV-2 spike antibody enzyme-linked immunosorbent assay and Roche Elecsys® anti-SARS-CoV-2 nucleocapsid antibody assays. Seropositivity was defined as SARS-CoV-2 antibodies on either (primary) or both (secondary) assays. Univariate Poisson regression assessed risk factors associated with seropositivity. The median age was 27.4 years, and HIV prevalence was 26.7%. SARS-CoV-2 seroprevalence was 64.0% (95% confidence interval [CI]: 59.6-68.2%) on the primary and 54% (95% CI: 49.5-58.4%) on the secondary measure. Most (96.6%) women who were SARS-CoV-2-seropositive reported no symptoms. On the Roche assay, we detected lower seroprevalence among women living with HIV than women without HIV (48.9% vs 61.7%, P -value = 0.018), and especially low levels among women living with HIV with a clusters of differentiation 4 <350 cells/ml compared with women without immune suppression (22.2% vs 56.4%, prevalence rate ratio = 0.4; 95% CI: 0.2-0.9; P -value = 0.046). Pregnant women attending routine antenatal care had a high SARS-CoV-2 seroprevalence after the second wave in South Africa, and most had asymptomatic infections. Seroprevalence surveys in pregnant women present a feasible method of monitoring the course of the pandemic over time. [ABSTRACT FROM AUTHOR]

ABSTRACT Serosurveys can determine the extent and spread of a pathogen in populations. However, collection of venous blood requires trained medical staff. Dried blood spots (DBS) are a suitable alternative because they can be self-collected and stored/shipped at room temperature. As COVID-19 vaccine deployment began in early 2021, we rapidly enrolled laboratory employees in a study to evaluate IgG antibody levels following vaccination. Participants received a DBS collection kit, self-collection instructions, and a brief questionnaire. Three DBS were collected by each of 168 participants pre- and/or postvaccination and tested with a multiplex microsphere immunoassay (MIA) that separately measures IgG antibodies to SARS-CoV-2 spike-S1 and nucleocapsid antigens. Most DBS (99.6%, 507/509) were suitable for testing. Participants with prior SARS-CoV-2 infection (n = 7) generated high S antibody levels after the first vaccine dose. Naïve individuals (n = 161) attained high S antibody levels after the second dose. Similar antibody levels were seen among those vaccinated with Moderna (n = 29) and Pfizer-BioNTech (n = 137). For those receiving either mRNA vaccine, local side effects were more common after the first vaccine dose, whereas systemic side effects were more common after the second dose. Individuals with the highest antibody levels in the week prior to the second vaccine dose experienced more side effects from the second dose. Our study demonstrated that combining self-collected DBS and a multiplex MIA is a convenient and effective way to assess antibody levels to vaccination and could easily be used for population serosurveys of SARS-CoV-2 or other emerging pathogens. IMPORTANCE Serosurveys are an essential tool for assessing immunity in a population (1, 2). However, common barriers to effective serosurveys, particularly during a pandemic, include high-costs, resources required to collect venous blood samples, lack of trained laboratory technicians, and time required to perform the assay. By utilizing self-collected dried blood spots (DBS) and our previously developed high-throughput microsphere immunoassay, we were able to significantly reduce many of these common challenges. Participants were asked to self-collect three DBS before and/or after they received their COVID-19 vaccines to measure antibody levels following vaccination. Participants successfully collected 507 DBS that were tested for IgG antibodies to the spike and nucleocapsid proteins of SARS-CoV-2. When used with self-collected DBS, our relatively low-cost assay significantly reduced common barriers to collecting serological data from a population and was able to effectively assess antibody response to vaccination.

Summary: Background: COVID-19 serosurveys allow for the monitoring of the level of SARS-CoV-2 transmission and support data-driven decisions. We estimated the seroprevalence of anti-SARS-CoV-2 antibodies in a large favela complex in Rio de Janeiro, Brazil. Methods: A population-based panel study was conducted in Complexo de Manguinhos (16 favelas) with a probabilistic sampling of participants aged ≥1 year who were randomly selected from a census of individuals registered in primary health care clinics that serve the area. Participants answered a structured interview and provided blood samples for serology. Multilevel regression models (with random intercepts to account for participants’ favela of residence) were used to assess factors associated with having anti-S IgG antibodies. Secondary analyses estimated seroprevalence using an additional anti-N IgG assay. Findings: 4,033 participants were included (from Sep/2020 to Feb/2021, 22 epidemic weeks), the median age was 39·8 years (IQR:21·8-57·7), 61% were female, 41% were mixed-race (Pardo) and 23% Black. Overall prevalence was 49·0% (95%CI:46·8%-51·2%) which varied across favelas (from 68·3% to 31·4%). Lower prevalence estimates were found when using the anti-N IgG assay. Odds of having anti-S IgG antibodies were highest for young adults, and those reporting larger household size, poor adherence to social distancing and use of public transportation. Interpretation: We found a significantly higher prevalence of anti-S IgG antibodies than initially anticipated. Disparities in estimates obtained using different serological assays highlight the need for cautious interpretation of serosurveys estimates given the heterogeneity of exposure in communities, loss of immunological biomarkers, serological antigen target, and variant-specific test affinity. Funding: Fundação Oswaldo Cruz, Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ), the European Union's Horizon 2020 research and innovation programme, Royal Society, Serrapilheira Institute, and FAPESP.

The extent of the COVID-19 pandemic will be better understood through serosurveys and SARS-CoV-2 antibody testing. Dried blood spot (DBS) samples will play a central role in large scale serosurveillance by simplifying biological specimen collection and transportation, especially in Canada. Direct comparative performance data on multiplex SARS-CoV-2 assays resulting from identical DBS samples are currently lacking. In our study, we aimed to provide performance data for the BioPlex 2200 SARS-CoV-2 IgG (Bio-Rad), V-PLEX SARS-CoV-2 Panel 2 IgG (MSD), and Elecsys Anti-SARS-CoV-2 (Roche) commercial assays, as well as for two highly scalable in-house assays (University of Ottawa and Mount Sinai Hospital protocols) to assess their suitability for DBS-based SARS-CoV-2 DBS serosurveillance. These assays were evaluated against identical panels of DBS samples collected from convalescent COVID-19 patients (n = 97) and individuals undergoing routine sexually transmitted and bloodborne infection (STBBI) testing prior to the COVID-19 pandemic (n = 90). Our findings suggest that several assays are suitable for serosurveillance (sensitivity >97% and specificity >98%). In contrast to other reports, we did not observe an improvement in performance using multiple antigen consensus-based rules to establish overall seropositivity. This may be due to our DBS panel which consisted of samples collected from convalescent COVID-19 patients with significant anti-spike, -receptor binding domain (RBD), and -nucleocapsid antibody titers. This study demonstrates that biological specimens collected as DBS coupled with one of several readily available assays are useful for large-scale COVID-19 serosurveillance.

A Vibrio cholerae O1 outbreak emerged in Haiti in October 2022 after years of cholera absence. In samples from a 2021 serosurvey, we found lower circulating antibodies against V. cholerae lipopolysaccharide in children <5 years of age and no vibriocidal antibodies, suggesting high susceptibility to cholera, especially among young children.

The article focuses on the efforts to eliminate measles virus by serosurveys and other diagnostic tools to determine the immunity gap involved. Topics discussed include disease eradication plan as per the organization World Health Organization (WHO), economics of conducting serosurveys, which includes logistics.

Serosurveys can determine the extent and spread of a pathogen in populations. However, collection of venous blood requires trained medical staff. Dried blood spots (DBS) are a suitable alternative because they can be self-collected and stored/shipped at room temperature. As COVID-19 vaccine deployment began in early 2021, we rapidly enrolled laboratory employees in a study to evaluate IgG antibody levels following vaccination. Participants received a DBS collection kit, self-collection instructions, and a brief questionnaire. Three DBS were collected by each of 168 participants pre- and/or postvaccination and tested with a multiplex microsphere immunoassay (MIA) that separately measures IgG antibodies to SARS-CoV-2 spike-S1 and nucleocapsid antigens. Most DBS (99.6%, 507/509) were suitable for testing. Participants with prior SARS-CoV-2 infection ( n  = 7) generated high S antibody levels after the first vaccine dose. Naïve individuals ( n  = 161) attained high S antibody levels after the second dose. Similar antibody levels were seen among those vaccinated with Moderna ( n  = 29) and Pfizer-BioNTech ( n  = 137). For those receiving either mRNA vaccine, local side effects were more common after the first vaccine dose, whereas systemic side effects were more common after the second dose. Individuals with the highest antibody levels in the week prior to the second vaccine dose experienced more side effects from the second dose. Our study demonstrated that combining self-collected DBS and a multiplex MIA is a convenient and effective way to assess antibody levels to vaccination and could easily be used for population serosurveys of SARS-CoV-2 or other emerging pathogens. IMPORTANCE Serosurveys are an essential tool for assessing immunity in a population (1, 2). However, common barriers to effective serosurveys, particularly during a pandemic, include high-costs, resources required to collect venous blood samples, lack of trained laboratory technicians, and time required to perform the assay. By utilizing self-collected dried blood spots (DBS) and our previously developed high-throughput microsphere immunoassay, we were able to significantly reduce many of these common challenges. Participants were asked to self-collect three DBS before and/or after they received their COVID-19 vaccines to measure antibody levels following vaccination. Participants successfully collected 507 DBS that were tested for IgG antibodies to the spike and nucleocapsid proteins of SARS-CoV-2. When used with self-collected DBS, our relatively low-cost assay significantly reduced common barriers to collecting serological data from a population and was able to effectively assess antibody response to vaccination.

Background: COVID-19 serosurveys allow for the monitoring of the level of SARS-CoV-2 transmission and support data-driven decisions. We estimated the seroprevalence of anti-SARS-CoV-2 antibodies in a large favela complex in Rio de Janeiro, Brazil., Methods: A population-based panel study was conducted in Complexo de Manguinhos (16 favelas ) with a probabilistic sampling of participants aged ≥1 year who were randomly selected from a census of individuals registered in primary health care clinics that serve the area. Participants answered a structured interview and provided blood samples for serology. Multilevel regression models (with random intercepts to account for participants' favela of residence) were used to assess factors associated with having anti-S IgG antibodies. Secondary analyses estimated seroprevalence using an additional anti-N IgG assay., Findings: 4,033 participants were included (from Sep/2020 to Feb/2021, 22 epidemic weeks), the median age was 39·8 years (IQR:21·8-57·7), 61% were female, 41% were mixed-race ( Pardo ) and 23% Black. Overall prevalence was 49·0% (95%CI:46·8%-51·2%) which varied across favelas (from 68·3% to 31·4%). Lower prevalence estimates were found when using the anti-N IgG assay. Odds of having anti-S IgG antibodies were highest for young adults, and those reporting larger household size, poor adherence to social distancing and use of public transportation., Interpretation: We found a significantly higher prevalence of anti-S IgG antibodies than initially anticipated. Disparities in estimates obtained using different serological assays highlight the need for cautious interpretation of serosurveys estimates given the heterogeneity of exposure in communities, loss of immunological biomarkers, serological antigen target, and variant-specific test affinity., Funding: Fundação Oswaldo Cruz, Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo a Pesquisa do Estado do Rio de Janeiro (FAPERJ), the European Union's Horizon 2020 research and innovation programme, Royal Society, Serrapilheira Institute, and FAPESP., Competing Interests: DAMV is an Ad-hoc member of the Committee on COVID-19 Immunization from the Ministry of Health; CJS participates I PAHO and WHO advisory Boards (unpaid). All authors declare no competing interests., (© 2022 The Authors.)

The extent of the COVID-19 pandemic will be better understood through serosurveys and SARS-CoV-2 antibody testing. Dried blood spot (DBS) samples will play a central role in large scale serosurveillance by simplifying biological specimen collection and transportation, especially in Canada. Direct comparative performance data on multiplex SARS-CoV-2 assays resulting from identical DBS samples are currently lacking. In our study, we aimed to provide performance data for the BioPlex 2200 SARS-CoV-2 IgG (Bio-Rad), V-PLEX SARS-CoV-2 Panel 2 IgG (MSD), and Elecsys Anti-SARS-CoV-2 (Roche) commercial assays, as well as for two highly scalable in-house assays (University of Ottawa and Mount Sinai Hospital protocols) to assess their suitability for DBS-based SARS-CoV-2 DBS serosurveillance. These assays were evaluated against identical panels of DBS samples collected from convalescent COVID-19 patients ( n = 97) and individuals undergoing routine sexually transmitted and bloodborne infection (STBBI) testing prior to the COVID-19 pandemic ( n = 90). Our findings suggest that several assays are suitable for serosurveillance (sensitivity >97% and specificity >98%). In contrast to other reports, we did not observe an improvement in performance using multiple antigen consensus-based rules to establish overall seropositivity. This may be due to our DBS panel which consisted of samples collected from convalescent COVID-19 patients with significant anti-spike, -receptor binding domain (RBD), and -nucleocapsid antibody titers. This study demonstrates that biological specimens collected as DBS coupled with one of several readily available assays are useful for large-scale COVID-19 serosurveillance., Competing Interests: The authors declare no conflict of interest., (Crown Copyright © 2022 Published by Elsevier Ltd.)

Household surveys remain an essential method for estimating vaccine coverage in developing countries. However, the resulting estimates have inevitable and currently unmeasurable information biases due to inaccuracies in recall, low retention of home-based records (HBRs; i.e., vaccination cards), and inaccurate recording of vaccination on HBRs. We developed an innovative method with which to overcome these biases, enhance the validity of survey results, and estimate true vaccine coverage using nested serological assessments of immune markers. We enrolled children aged 12-23 months in vaccine coverage surveys in Karachi, Pakistan, from January to December 2016. Vaccination history was collected through verbal recall by the caregiver and, when available, by HBR. One-third of survey participants were randomly enrolled for serological testing for anti-measles virus immunoglobulin G antibody. We applied Bayesian latent class models to evaluate the misalignment among measles vaccination histories derived by recall, HBRs, and measles serology and estimated true measles vaccine coverage. The model-based estimate of true measles vaccine coverage was 61.1% (95% credible interval: 53.5, 69.4) among all survey participants. The standard estimate of 73.2% (95% confidence interval: 71.3, 75.1) defined by positive recall or HBR documentation substantially overestimated the vaccine coverage. Researchers can correct for information biases using serological assessments in a subsample of survey participants and latent class analytical approaches., (© The Author(s) 2019. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)