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BackgroundMany studies report the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. We aimed to synthesize seroprevalence data to better estimate the level and distribution 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 December 31, 2020. We included studies that reported a sample size, study date, location, and seroprevalence estimate. We corrected estimates for imperfect test accuracy with Bayesian measurement error models, 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.ResultsWe identified 968 seroprevalence studies including 9.3 million participants in 74 countries. There were 472 studies (49%) at low or moderate risk of bias. Seroprevalence was low in the general population (median 4.5%, IQR 2.4–8.4%); however, it varied widely in specific populations from low (0.6% perinatal) to high (59% persons in assisted living and long-term care facilities). Median seroprevalence also varied by Global Burden of Disease region, from 0.6% in Southeast Asia, East Asia and Oceania to 19.5% in Sub-Saharan Africa (pDiscussionMost of the population remains susceptible to SARS-CoV-2 infection. Public health measures must be improved to protect disproportionately affected groups, including racial and ethnic minorities, until vaccine-derived herd immunity is achieved. Improvements in serosurvey design and reporting are needed for ongoing monitoring of infection prevalence and the pandemic response.

BackgroundMany studies report the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies. We aimed to synthesize seroprevalence data to better estimate the level and distribution 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 December 31, 2020. We included studies that reported a sample size, study date, location, and seroprevalence estimate. We corrected estimates for imperfect test accuracy with Bayesian measurement error models, 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.ResultsWe identified 968 seroprevalence studies including 9.3 million participants in 74 countries. There were 472 studies (49%) at low or moderate risk of bias. Seroprevalence was low in the general population (median 4.5%, IQR 2.4-8.4%); however, it varied widely in specific populations from low (0.6% perinatal) to high (59% persons in assisted living and long-term care facilities). Median seroprevalence also varied by Global Burden of Disease region, from 0.6 % in Southeast Asia, East Asia and Oceania to 19.5% in Sub-Saharan Africa (pDiscussionMost of the population remains susceptible to SARS-CoV-2 infection. Public health measures must be improved to protect disproportionately affected groups, including racial and ethnic minorities, until vaccine-derived herd immunity is achieved. Improvements in serosurvey design and reporting are needed for ongoing monitoring of infection prevalence and the pandemic response.FundingPublic Health Agency of Canada through the COVID-19 Immunity Task Force.

Background An outbreak of highly pathogenic avian influenza (HPAI) between 2004 and 2006 resulted in the culling of 45 million birds, and has jeopardised sustainable agricultural production in southeast Asia. HPAI is highly virulent, and small-scale farms present a high-risk environment for disease transmission between animals and humans. The purpose of this study was to investigate how attitudes towards HPAI influence biosecurity mitigation behaviours such as water source management and sanitation on small-scale farms in Vietnam. Methods We used a participatory approach that included representation from farmers, government, academia, and industry. We collected cross-sectional data on demographics, farm level production, and attitudes and preferences with respect to HPAI and mitigation strategies in north and south Vietnam (Thai Binh and An Giang Provinces, respectively). A stratified randomised selection of 600 small-scale mixed livestock, crop, and fish farmers were interviewed using questionnaires and in-person interviews. We calculated participant numbers using standard epidemiological sample size formulae with α=0·05. The study was approved by Canadian and Vietnamese ethics boards and participants provided verbal informed consent. Logit regression analysis was used to examine the relation between factors influencing HPAI attitudes and behaviours. Further correlation analysis is under investigation, including Pearson correlation and principal component analysis. Findings Preliminary results show that half the farmers (51%, n=306) did not treat their water according to UN Food and Agriculture Organization guidelines, and fewer than 7% (n=40) said they would report a suspected HPAI case because of the cost and inconvenience of doing so. However, those farmers who expressed concern about HPAI were more likely to practise mitigation behaviours (p=0·034). Interpretation These preliminary analyses indicate that biosecurity guidelines may not be consistent with management styles of small-scale farms in Vietnam, but also indicate cause for concern for controlling HPAI on such farms. These results should be of interest to public health and policy authorities addressing HPAI mitigation. Our results may not be generalisable to all small-scale farmers in Vietnam because water sources and farming strategies vary across communes. Funding Grand Challenges Canada (Grant Number 0231-01 Stars in Global Health Round 4) and IDRC, Ottawa.