SARS-CoV-2 seroprevalence worldwide: a systematic review and meta-analysis

Abstract

Objectives: COVID-19 has been arguably the most important public health concern worldwide in 2020, and efforts are now escalating to suppress or eliminate its spread. In this study we undertook a meta-analysis to estimate the global and regional seroprevalence rates in humans of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and to assess whether seroprevalence is associated with geographical, climatic and/or sociodemographic factors.

Methods: We systematically reviewed PubMed, Scopus, Embase, medRxiv and bioRxiv databases for preprints or peer-reviewed articles (up to 14 August 2020). Study eligibility criteria were population-based studies describing the prevalence of anti-SARS-CoV-2 (IgG and/or IgM) serum antibodies. Participants were people from different socioeconomic and ethnic backgrounds (from the general population), whose prior COVID-19 status was unknown and who were tested for the presence of anti-SARS-CoV-2 serum antibodies. We used a random-effects model to estimate pooled seroprevalence, and then extrapolated the findings to the global population (for 2020). Subgroup and meta-regression analyses explored potential sources of heterogeneity in the data, and relationships between seroprevalence and sociodemographic, geographical and/or climatic factors.

Results: In total, 47 studies involving 399 265 people from 23 countries met the inclusion criteria. Heterogeneity (I² = 99.4%, p < 0.001) was seen among studies; SARS-CoV-2 seroprevalence in the general population varied from 0.37% to 22.1%, with a pooled estimate of 3.38% (95%CI 3.05-3.72%; 15 879/399 265). On a regional level, seroprevalence varied from 1.45% (0.95-1.94%, South America) to 5.27% (3.97-6.57%, Northern Europe), although some variation appeared to relate to the serological assay used. The findings suggested an association of seroprevalence with income levels, human development indices, geographic latitudes and/or climate. Extrapolating to the 2020 world population, we estimated that 263.5 million individuals had been exposed or infected at the time of this study.

Conclusions: This study showed that SARS-CoV-2 seroprevalence varied markedly among geographic regions, as might be expected early in a pandemic. Longitudinal surveys to continually monitor seroprevalence around the globe will be critical to support prevention and control efforts, and might indicate levels of endemic stability or instability in particular countries and regions.

Keywords: COVID-19; General population; Global seroprevalence; Meta-analysis; SARS-CoV-2; Serum antibodies (IgG and/or IgM); Subgroup analyses.

Fig. 1

Search strategy and study selection process, indicating numbers of studies (and associated datasets) excluded or included.

Fig. 2

Estimated seroprevalence rates of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the general human population in different countries using the geographic information system (GIS).

Fig. 3

Ecological random effects meta-regression analyses of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence in the general population in relation to: (A) a country's income level (a statistically significant upward trend in seroprevalence in countries with higher income levels); (B) human development index (HDI) (a statistically significant upward trend in seroprevalence in higher HDI countries); (C) geographical latitude (a statistically significant upward trend in seroprevalence with increasing geographical latitude); and (D) the mean temperature during study implementation (a statistically significant downward trend in seroprevalence with increasing mean temperature).

Fig. 4

Random effects meta-regression analysis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) seroprevalence in the general human population in relation to time from the start of the pandemic to the time of sampling/testing in individual studies (articles) included in the present review. A statistically significant upward trend in seroprevalence is seen over time (C = 0.002, p 0.02).