Adherence of SARS-CoV-2 seroepidemiologic studies to the ROSES-S reporting guideline during the COVID-19 pandemic (preprint)

BackgroundComplete reporting of seroepidemiologic studies (e.g. sampling and measurement methods, immunoassay characteristics) are critical to their interpretation, comparison, and utility in evidence synthesis. The Reporting of Seroepidemiologic studies--SARS_JCoV_J2 (ROSES-S) guideline is a reporting checklist that aims to improve the quality and transparency of reporting in SARS-CoV-2 seroepidemiological studies. While the synthesis of seroepidemiologic studies played a crucial role in public health decision-making during the COVID-19 pandemic, adherence of SARS-CoV-2 seroepidemiologic studies to the ROSES-S guideline has not yet been evaluated. ObjectivesTo evaluate the completeness of SARS-CoV-2 seroepidemiologic study reporting over the first two years of the COVID-19 pandemic by assessing adherence to the ROSES-S reporting guideline, determine whether publication of the ROSES-S guideline was associated with changes in reporting completeness, and identify study characteristics associated with reporting completeness. MethodsA stratified random sample of SARS-CoV-2 seroepidemiologic studies from the SeroTracker living systematic review database was evaluated for adherence to the ROSES-S guideline. We categorized study adherence to each reporting item in the guideline as "reported", "not reported", or "not applicable". For each reporting item we calculated the percentage of studies that were adherent. We also calculated the median and interquartile range (IQR) adherence across all items and by item domain. Piecewise and multivariable beta regression analyses were used to determine whether publication date of the ROSES-S guideline was associated with changes in the overall adherence scores and to identify study characteristics associated with overall adherence scores. Results199 studies were included and analyzed. The median adherence to reporting items was 48.1% (IQR 40.0%-55.2%) per study. Adherence to reporting items ranged from 8.8% to 72.7% per study. The laboratory methods domain (e.g. description of testing algorithm) had the lowest median adherence (33.3% [IQR 25.0%-41.7%%]), while the discussion domain had the highest median adherence (75.0% [IQR 50.0%-100.0%])). There were no significant changes in reporting adherence to ROSES-S before and after guideline publication. Article publication source (p<0.001), study risk of bias (p=0.001), and sampling method (p=0.004) were significantly associated with adherence to the ROSES-S guideline. ConclusionsThe completeness of reporting in SARS-CoV-2 seroepidemiologic studies was suboptimal, especially in laboratory methods, and was associated with key study characteristics. Publication of the ROSES-S guideline was not associated with changes in reporting practices. Given that reporting is necessary to improve the standardization and utility of seroprevalence data in evidence synthesis, authors should improve adherence to the ROSES-S guideline with support from stakeholders.

Serology assays used in SARS-CoV-2 seroprevalence surveys worldwide: a systematic review and meta-analysis of assay features, testing algorithms, and performance (preprint)

Background: Many SARS-CoV-2 serological assays were rapidly developed during the COVID-19 pandemic. However, differences in detection mechanism limit the comparability of assay outputs. Methods: As part of the SeroTracker global living systematic review of SARS-CoV-2 seroprevalence studies, we collated serological assays used in serosurveys between January 1, 2020 and November 19, 2021. We mapped performance metrics to the manufacturer, third-party head-to-head, and independent group evaluations, comparing the assay performance data using a mixed-effect beta regression model. Results: Among 1807 serosurveys, 192 distinctive commercial assays and 380 self-developed assays were identified. According to manufacturers, 28.6% of all commercial assays met WHO criteria for emergency use (sensitivity [Sn.] >= 90.0%, specificity [Sp.] >= 97.0%). Third-party and independent evaluations indicated that manufacturers overstated the Sn. of their assays by 5.4% and 2.8%, and Sp. by 6.3% and 1.2%. We found in simulations that inaccurate Sn. and Sp. can substantially bias seroprevalence estimates corrected for assay performance. Conclusions: The Sn. and Sp. of the serological assay are not fixed properties, but varying features depending on testing population. To achieve precise population estimates and to ensure comparability, serosurveys should select assays with strong, independently validated performance and adjust seroprevalence estimates based on assured performance data.

Protective effectiveness of prior SARS-CoV-2 infection and hybrid immunity against Omicron infection and severe disease: a systematic review and meta-regression (preprint)

Background We aimed to systematically review the magnitude and duration of the protective effectiveness of prior infection (PE) and hybrid immunity (HE) against Omicron infection and severe disease. Methods We searched pre-print and peer-reviewed electronic databases for controlled studies from January 1, 2020, to June 1, 2022. Risk of bias (RoB) was assessed using the Risk of Bias In Non-Randomized Studies of Interventions (ROBINS-I)-Tool. We used random-effects meta-regression to estimate the magnitude of protection at 1-month intervals and the average change in protection since the last vaccine dose or infection from 3 months to 6 or 12 months. We compared our estimates of PE and HE to previously published estimates of the magnitude and durability of vaccine effectiveness (VE) against Omicron. Findings Eleven studies of prior infection and 15 studies of hybrid immunity were included. For prior infection, there were 97 estimates (27 at moderate RoB and 70 at serious RoB), with the longest follow up at 15 months. PE against hospitalization or severe disease was 82.5% [71.8-89.7%] at 3 months, and 74.6% [63.1-83.5%] at 12 months. PE against reinfection was 65.2% [52.9-75.9%] at 3 months, and 24.7% [16.4-35.5%] at 12 months. For HE, there were 153 estimates (78 at moderate RoB and 75 at serious RoB), with the longest follow up at 11 months for primary series vaccination and 4 months for first booster vaccination. Against hospitalization or severe disease, HE involving either primary series vaccination or first booster vaccination was consistently >95% for the available follow up. Against reinfection, HE involving primary series vaccination was 69.0% [58.9-77.5%] at 3 months after the most recent infection or vaccination, and 41.8% [31.5-52.8%] at 12 months, while HE involving first booster vaccination was 68.6% [58.8-76.9%] at 3 months, and 46.5% [36.0-57.3%] at 6 months. Against hospitalization or severe disease at 6 months, hybrid immunity with first booster vaccination (effectiveness 95.3% [81.9-98.9%]) or with primary series alone (96.5% [90.2-98.8%]) provided significantly greater protection than prior infection alone (80.1% [70.3-87.2%]), first booster vaccination alone (76.7% [72.5-80.4%]), or primary series alone (64.6% [54.5-73.6%]). Results for protection against reinfection were similar. Interpretation Prior infection and hybrid immunity both provided greater and more sustained protection against Omicron than vaccination alone. All protection estimates waned quickly against infection but remained high for hospitalisation or severe disease. Individuals with hybrid immunity had the highest magnitude and durability of protection against all outcomes, reinforcing the global imperative for vaccination.

Development of the Quality of Teen Trauma Acute Ca­re Patient and Parent-Reported Experience Measure (preprint)

Objective: Patient-Reported Experience Measures (PREMs) provide valuable patient feedback on quality of care and have been associated with clinical outcomes. We tested the reliability of a modified version of an adult trauma PREM on injured adolescents and their parents, adding questions on school, social, and family accommodation. Results: : Test-retest reliability was assessed using Cohen’s kappa, weighted kappa, and percent agreement between responses. Directionality of changed responses was noted. Most of the study ran during the COVID-19 pandemic. We identified poorer reliability among constructs that varied from the norm during the pandemic, including maintenance of social networks, need of supports for school and follow-up care. Parents appeared to have more directionality of change of responses with reporting more negative in-hospital and more positive post-discharge experiences over time between the test and retest. Situational factors due to the COVID-19 pandemic and potential risks of recall bias may have limited the reliability of some parts of the survey. Retesting of this new PREM instrument outside of the context of the COVID-19 pandemic as well as delivering it in 2 phases to reduce the risk of recall bias may result in stronger reliability of the tool.

A real-world evaluation of the implementation of NLP technology in abstract screening of a systematic review (preprint)

The laborious and time-consuming nature of systematic review production hinders the dissemination of up-to-date evidence synthesis. Well-performing natural language processing (NLP) tools for systematic reviews have been developed, showing promise to improve efficiency. However, the feasibility and value of these technologies have not been comprehensively demonstrated in a real-world review. We developed an NLP-assisted abstract screening tool that provides text inclusion recommendations, keyword highlights, and visual context cues. We evaluated this tool in a living systematic review on SARS-CoV-2 seroprevalence, conducting a quality improvement assessment of screening with and without the tool. We evaluated changes to abstract screening speed, screening accuracy, characteristics of included texts, and user satisfaction. The tool improved efficiency, reducing screening time per abstract by 45.9% and decreasing inter-reviewer conflict rates. The tool conserved precision of article inclusion (positive predictive value; 0.92 with tool vs 0.88 without) and recall (sensitivity; 0.90 vs 0.81). The summary statistics of included studies were similar with and without the tool. Users were satisfied with the tool (mean satisfaction score of 4.2 / 5). We evaluated an abstract screening process where one human reviewer was replaced with the tool’s votes, finding that this maintained recall (0.92 one-person, one-tool vs 0.90 two tool-assisted humans) and precision (0.91 vs 0.92) while reducing screening time by 70%. Implementing an NLP tool in this living systematic review improved efficiency, maintained accuracy, and was well-received by researchers, demonstrating the real-world effectiveness of NLP in expediting evidence synthesis.

Timeliness of reporting of SARS-CoV-2 seroprevalence results and their utility for infectious disease surveillance (preprint)

Seroprevalence studies have been used throughout the COVID-19 pandemic to monitor infection and immunity. These studies are often reported in peer-reviewed journals, but the academic writing and publishing process can delay reporting and thereby public health action. Seroprevalence estimates have been reported faster in preprints and media, but with concerns about data quality. We aimed to (i) describe the timeliness of SARS-CoV-2 serosurveillance reporting by publication venue and study characteristics and (ii) identify relationships between timeliness, data validity, and representativeness to guide recommendations for serosurveillance efforts. We included seroprevalence studies published between January 1, 2020 and December 31, 2021 from the ongoing SeroTracker living systematic review. For each study, we calculated timeliness as the time elapsed between the end of sampling and the first public report. We evaluated data validity based on serological test performance and correction for sampling error, and representativeness based on use of a representative sample frame and adequate sample coverages. We examined how timeliness varied with study characteristics, representativeness, and data validity using univariate and multivariate Cox regression. We analyzed 1,844 studies. Median time to publication was 154 days (IQR 64-255), varying by publication venue (journal articles: 212 days, preprints: 101 days, institutional reports: 18 days, and media: 12 days). Multivariate analysis confirmed the relationship between timeliness and publication venue and showed that general population studies were published faster than special population or health care worker studies; there was no relationship between timeliness and study geographic scope, geographic region, representativeness, or serological test performance. Seroprevalence studies in peer-reviewed articles and preprints are published slowly, highlighting the limitations of using the academic literature to report seroprevalence during a health crisis. More timely reporting of seroprevalence estimates can improve their usefulness for surveillance, enabling more effective responses during health emergencies.

SARS-CoV-2 infection in Africa: A systematic review and meta-analysis of standardised seroprevalence studies, from January 2020 to December 2021 (preprint)

IntroductionEstimating COVID-19 cumulative incidence in Africa remains problematic due to challenges in contact tracing, routine surveillance systems and laboratory testing capacities and strategies. We undertook a meta-analysis of population-based seroprevalence studies to estimate SARS-CoV-2 seroprevalence in Africa to inform evidence-based decision making on Public Health and Social Measures (PHSM) and vaccine strategy. MethodsWe searched for seroprevalence studies conducted in Africa published 01-01-2020 to 30-12-2021 in Medline, Embase, Web of Science, and Europe PMC (preprints), grey literature, media releases and early results from WHO Unity studies. All studies were screened, extracted, assessed for risk of bias and evaluated for alignment with the WHO Unity protocol for seroepidemiological investigations. We conducted descriptive analyses of seroprevalence and meta-analysed seroprevalence differences by demographic groups, place and time. We estimated the extent of undetected infections by comparing seroprevalence and cumulative incidence of confirmed cases reported to WHO. PROSPERO: CRD42020183634. ResultsWe identified 54 full texts or early results, reporting 151 distinct seroprevalence studies in Africa Of these, 95 (63%) were low/moderate risk of bias studies. SARS-CoV-2 seroprevalence rose from 3.0% [95% CI: 1.0-9.2%] in Q2 2020 to 65.1% [95% CI: 56.3-73.0%] in Q3 2021. The ratios of seroprevalence from infection to cumulative incidence of confirmed cases was large (overall: 97:1, ranging from 10:1 to 958:1) and steady over time. Seroprevalence was highly heterogeneous both within countries - urban vs. rural (lower seroprevalence for rural geographic areas), children vs. adults (children aged 0-9 years had the lowest seroprevalence) - and between countries and African sub-regions (Middle, Western and Eastern Africa associated with higher seroprevalence). ConclusionWe report high seroprevalence in Africa suggesting greater population exposure to SARS-CoV-2 and protection against COVID-19 disease than indicated by surveillance data. As seroprevalence was heterogeneous, targeted PHSM and vaccination strategies need to be tailored to local epidemiological situations.

Global epidemiology of SARS-CoV-2 infection: a systematic review and meta-analysis of standardized population-based seroprevalence studies, Jan 2020-Oct 2021 (preprint)

Background COVID-19 case data underestimates infection and immunity, especially in low- and middle-income countries (LMICs). We meta-analyzed standardized SARS-CoV-2 seroprevalence studies to estimate global seroprevalence. Objectives/Methods We conducted a systematic review and meta-analysis, searching MEDLINE, Embase, Web of Science, preprints, and grey literature for SARS-CoV-2 seroprevalence studies aligned with the WHO UNITY protocol published between 2020-01-01 and 2021-10-29. Eligible studies were extracted and critically appraised in duplicate. We meta-analyzed seroprevalence by country and month, pooling to estimate regional and global seroprevalence over time; compared seroprevalence from infection to confirmed cases to estimate under-ascertainment; meta-analyzed differences in seroprevalence between demographic subgroups; and identified national factors associated with seroprevalence using meta-regression. PROSPERO: CRD42020183634. Results We identified 396 full texts reporting 736 distinct seroprevalence studies (41% LMIC), including 355 low/moderate risk of bias studies with national/sub-national scope in further analysis. By April 2021, global SARS-CoV-2 seroprevalence was 26.1%, 95% CI [24.6-27.6%]. Seroprevalence rose steeply in the first half of 2021 due to infection in some regions (e.g., 18.2% to 45.9% in Africa) and vaccination and infection in others (e.g., 11.3% to 57.4% in the Americas high-income countries), but remained low in others (e.g., 0.3% to 1.6% in the Western Pacific). In 2021 Q1, median seroprevalence to case ratios were 1.9:1 in HICs and 61.9:1 in LMICs. Children 0-9 years and adults 60+ were at lower risk of seropositivity than adults 20-29. In a multivariate model using data pre-vaccination, more stringent public health and social measures were associated with lower seroprevalence. Conclusions Global seroprevalence has risen considerably over time and with regional variation, however much of the global population remains susceptible to SARS-CoV-2 infection. True infections far exceed reported COVID-19 cases. Standardized seroprevalence studies are essential to inform COVID-19 control measures, particularly in resource-limited regions.

SeroTracker-ROB: reproducible decision rules for risk of bias assessment of seroprevalence studies (preprint)

BackgroundEvaluating seroprevalence study risk of bias (RoB) is crucial for robust infection surveillance, but can be a time-consuming and subjective process. We aimed to develop decision rules for reproducible RoB assessment and an automated tool to implement these decision rules. MethodsWe developed the SeroTracker-RoB approach to RoB assessment. To do so, we created objective criteria for items on the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Prevalence Studies and developed decision rules for RoB based on these items. The criteria and decision rules were based on published guidance for assessing RoB for prevalence studies and expert opinion. Decision rules were validated against the SeroTracker database of seroprevalence studies, which included consensus manual RoB judgements from two independent reviewers. We measured efficiency by calculating paired-samples t-test for time to judge RoB using the automated tool versus manually for 25 randomly selected articles from the SeroTracker database, coverage as the proportion of database studies where the decision rules could evaluate RoB, and reliability by calculating intraclass correlations between automated and manual RoB assessments. ResultsWe established objective criteria for seven of nine JBI items. We developed a set of decision rules with 61 branches. The SeroTracker-RoB tool was significantly faster than manual assessment with a mean time of 0.80 vs. 2.93 minutes per article (p<0.001), classified 100% (n = 2,070) of studies, and had good reliability compared to manual review (intraclass correlation 0.77, 95% confidence interval 0.74 to 0.80). The SeroTracker-RoB Excel Tool embeds this approach in a simple data extraction sheet for use by other researchers. ConclusionsThe SeroTracker-RoB approach was faster than manual assessment, with complete coverage and good reliability compared to two independent human reviewers. This approach and tool enable rapid, transparent, and reproducible evidence synthesis of infection prevalence studies, and may support public health efforts during future outbreaks and pandemics. O_TEXTBOXWhat is new? O_LIWhat is already known: Risk of bias assessments are a core element of evidence synthesis but can be time consuming and subjective. As such, there is a need for validated and transparent tools to automate such assessments, particularly during disease outbreaks and pandemics to inform public health decision making. However, there are currently no automated tools for risk of bias assessment of prevalence studies. C_LIO_LIWhat is new: We developed a reproducible approach to risk of bias assessment for SARS-CoV-2 seroprevalence studies. The automated approach was five times faster than manual human assessment, successfully categorized all 2,070 studies that it was tested on, and had good agreement with manual review. We built a simple Excel tool so that other researchers can use this automated approach. C_LIO_LIPotential impact: The SeroTracker-RoB approach and tool enables rapid, transparent, and reproducible risk of bias assessments for SARS-CoV-2 seroprevalence studies, and could be readily adapted for other types of disease prevalence studies. This process may also be applicable to automation of critical appraisal and risk of bias assessment for other types of studies and in other scientific disciplines. C_LI C_TEXTBOX

SARS-CoV-2 shedding dynamics across the respiratory tract, sex and disease severity for adult and pediatric COVID-19 (preprint)

Background SARS-CoV-2 shedding dynamics influence the risk of transmission and clinical manifestations of COVID-19. Yet, the relationships between SARS-CoV-2 shedding dynamics in the upper (URT) and lower respiratory tract (LRT) and age, sex and COVID-19 severity remain unclear. Methods Using systematic review, we developed a dataset of case characteristics (age, sex and COVID-19 severity) and quantitative respiratory viral loads (rVLs). We then conducted stratified analyses to assess SARS-CoV-2 shedding across disease course, COVID-19 severity, the respiratory tract, sex and age groups (aged 0 to 17 years, 18 to 59 years, and 60 years or older). Results The systematic dataset included 1,266 adults and 136 children with COVID-19. In the URT, adults with severe COVID-19 had higher rVLs at 1 day from symptom onset (DFSO) than adults ( P = 0.005) or children ( P = 0.017) with nonsevere illness. Between 1-10 DFSO, severe adults had comparable rates of SARS-CoV-2 clearance from the URT as nonsevere adults ( P = 0.479) and nonsevere children ( P = 0.863). In the LRT, severe adults showed higher rVLs post-symptom onset than nonsevere adults ( P = 0.006). In the analyzed period (4-10 DFSO), severely affected adults had no significant trend in SARS-CoV-2 clearance from LRT ( P = 0.105), whereas nonsevere adults showed a clear trend ( P < 0.001). After stratifying for disease severity, sex and age (including child vs. adult) were not predictive of the duration of respiratory shedding. The estimated accuracy for using URT shedding as a prognostic indicator for COVID-19 severity was up to 65%, whereas it was up to 81% for LRT shedding. Conclusions High, persistent LRT shedding of SARS-CoV-2 characterized severe COVID-19 in adults. After symptom onset, severe cases tended to have slightly higher URT shedding than their nonsevere counterparts. Disease severity, rather than age or sex, predicted SARS-CoV-2 kinetics. LRT specimens more accurately prognosticate COVID-19 severity than do URT specimens. Funding Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant, NSERC Senior Industrial Research Chair and the Toronto COVID-19 Action Fund.

Global seroprevalence of SARS-CoV-2 antibodies: a systematic review and meta-analysis (preprint)

BackgroundStudies reporting estimates of the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies have rapidly emerged. We aimed to synthesize seroprevalence data to better estimate the burden of SARS-CoV-2 infection, identify high-risk groups, and inform public health decision making. MethodsIn this systematic review and meta-analysis, we searched publication databases, preprint servers, and grey literature sources for seroepidemiological study reports, from January 1, 2020 to August 28, 2020. We included studies that reported a sample size, study date, location, and seroprevalence estimate. Estimates were corrected for imperfect test accuracy with Bayesian measurement error models. We conducted meta-analysis to identify demographic differences in the prevalence of SARS-CoV-2 antibodies, and meta-regression to identify study-level factors associated with seroprevalence. We compared region-specific seroprevalence data to confirmed cumulative incidence. PROSPERO: CRD42020183634. FindingsWe identified 338 seroprevalence studies including 2.3 million participants in 50 countries. Seroprevalence was low in the general population (median 3.2%, IQR 1.0-6.4%) and slightly higher in at-risk populations (median 5.4%, IQR 1.5-18.4%). Median seroprevalence varied by WHO Global Burden of Disease region (p < 0.01), from 1.0% in Southeast Asia, East Asia and Oceania to 18.8% in South Asia. National studies had lower seroprevalence estimates than local (p = 0.02) studies. Compared to White persons, Black persons (prevalence ratio [RR] 2.34, 95% CI 1.60-3.43) and Asian persons (RR 1.56, 95% CI 1.22-2.01) were more likely to be seropositive. Seroprevalence was higher among people ages 18-64 compared to 65 and over (RR 1.26, 95% CI 1.04-1.52). Health care workers had a 1.74x (95% CI: 1.18-2.58) higher risk compared to the general population. There was no difference in seroprevalence between sexes. There were 123 studies (36%) at low or moderate risk of bias. Seroprevalence estimates from national studies were median 11.9 (IQR 8.0 - 16.6) times higher than the corresponding SARS-CoV-2 cumulative incidence. InterpretationMost of the population remains susceptible to SARS-CoV-2 infection. Public health measures must be improved to protect disproportionately affected groups, including non-White people and adults. Measures taken in SE Asia, E Asia and Oceania, and Latin America and Caribbean may have been more effective in controlling virus transmission than measures taken in other regions. FundingPublic Health Agency of Canada through the COVID-19 Immunity Task Force.

Heterogeneity in transmissibility and shedding SARS-CoV-2 via droplets and aerosols (preprint)

A growing number of studies provide insight into how SARS-CoV-2 spreads1-7. Yet, many factors that characterize its transmissibility remain unclear, including mechanistic correlates of overdispersion, viral kinetics, the extent to which respiratory droplets and aerosols carry viable virus and the infectiousness of asymptomatic, presymptomatic and pediatric cases7. Here, we developed a comprehensive dataset of respiratory viral loads (rVLs) via systematic review and investigated these factors using meta-analyses and modeling. By comparing cases of COVID-19, SARS and influenza A(H1N1)pdm09, we found that heterogeneity in rVL was associated with overdispersion and facilitated the distinctions in individual variation in infectiousness among these emergent diseases. For COVID-19, case heterogeneity was broad throughout the infectious period, although rVL tended to peak at 1 day from symptom onset (DFSO) and be elevated for 1-5 DFSO. While most cases presented minimal risk, highly infectious ones could spread SARS-CoV-2 by talking, singing or breathing, which shed virions at comparable rates via droplets and aerosols. Coughing shed considerable quantities of virions, predominantly via droplets, and greatly increased the contagiousness of many symptomatic cases relative to asymptomatic ones. Asymptomatic and symptomatic infections showed similar likelihoods of expelling aerosols with SARS-CoV-2, as did adult and pediatric cases. Children tended to be less contagious by droplet spread than adults based on tendencies of symptomatology rather than rVL. Our findings address longstanding questions on SARS-CoV-2 transmissibility and present pertinent considerations for disease control.

Lessons from a rapid systematic review of early SARS-CoV-2 serosurveys (preprint)

Background. As the world grapples with the COVID-19 pandemic, there is increasing global interest in the role of serological testing for population monitoring and to inform public policy. However, limitations in serological study designs and test standards raise concerns about the validity of seroprevalence estimates and their utility in decision-making. There is now a critical window of opportunity to learn from early SARS-CoV-2 serology studies. We aimed to synthesize the results of SARS-CoV-2 serosurveillance projects from around the world and provide recommendations to improve the coordination, strategy, and methodology of future serosurveillance efforts. Methods. This was a rapid systematic review of cross-sectional and cohort studies reporting seroprevalence outcomes for SARS-CoV 2. We included completed, ongoing, and proposed serosurveys. The search included electronic databases (PubMed, MedRXIV, BioRXIV, and WHO ICTPR); five medical journals (NEJM, BMJ, JAMA, The Lancet, Annals of Internal Medicine); reports by governments, NGOs, and health systems; and media reports (Google News) from December 1, 2019 to May 1, 2020. We extracted data on study characteristics and critically appraised prevalence estimates using Joanna Briggs Institute criteria. Results. Seventy records met inclusion criteria, describing 73 studies. Of these, 23 reported prevalence estimates: eight preprints, 14 news articles, and one government report. These studies had a total sample size of 35,784 and reported 42 prevalence estimates. Seroprevalence estimates ranged from 0.4% to 59.3%. No estimates were found to have a low risk of bias (43% high risk, 21% moderate risk, 36% unclear). Fifty records reported characteristics of ongoing or proposed serosurveys. Overall, twenty countries have completed, ongoing, or proposed serosurveys. Discussion. Study design, quality, and prevalence estimates of early SARS-CoV2 serosurveys are heterogeneous, suggesting that the urgency to examine seroprevalence may have compromised methodological rigour. Based on the limitations of included studies, future serosurvey investigators and stakeholders should ensure that: i) serological tests used undergo high-quality independent evaluations that include cross-reactivity; ii) all reports of serosurvey results, including media, describe the test used, sample size, and sampling method; and iii) initiatives are coordinated to prevent test fatigue, minimize redundant efforts, and encourage better study methodology. Other. PROSPERO: CRD42020183634. No third-party funding.