Update on SARS-CoV-2 seroprevalence: regional and worldwide

Abstract

Background: With limited vaccine supplies, an informed position on the status of SARS-CoV-2 infection in people can assist the prioritization of vaccine deployment.

Objectives: We performed a systematic review and meta-analysis to estimate the global and regional SARS-CoV-2 seroprevalences around the world.

Data sources: We systematically searched peer-reviewed databases (PubMed, Embase and Scopus), and preprint servers (medRxiv, bioRxiv and SSRN) for articles published between 1 January 2020 and 30 March 2021.

Study eligibility criteria: Population-based studies reporting the SARS-CoV-2 seroprevalence in the general population were included.

Participants: People of different age groups, occupations, educational levels, ethnic backgrounds and socio-economic status from the general population.

Interventions: There were no interventions.

Methods: We used the random-effects meta-analyses and empirical Bayesian method to estimate the pooled seroprevalence and conducted subgroup and meta-regression analyses to explore potential sources of heterogeneity as well as the relationship between seroprevalence and socio-demographics.

Results: We identified 241 eligible studies involving 6.3 million individuals from 60 countries. The global pooled seroprevalence was 9.47% (95% CI 8.99-9.95%), although the heterogeneity among studies was significant (I² = 99.9%). We estimated that ∼738 million people had been infected with SARS-CoV-2 (as of December 2020). Highest and lowest seroprevalences were recorded in Central and Southern Asia (22.91%, 19.11-26.72%) and Eastern and South-eastern Asia (1.62%, 1.31-1.95%), respectively. Seroprevalence estimates were higher in males, persons aged 20-50 years, in minority ethnic groups living in countries or regions with low income and human development indices.

Conclusions: The present study indicates that the majority of the world's human population was still highly susceptible to SARS-CoV-2 infection in mid-2021, emphasizing the need for vaccine deployment to vulnerable groups of people, particularly in developing countries, and for the implementation of enhanced preventive measures until 'herd immunity' to SARS-CoV-2 has developed.

Keywords: General population; Meta-analysis; SARS-CoV-2; Seroprevalence; Serum antibodies; Subgroup analyses.

Fig. 1

Flowchart of the search strategy and study selection process of SARS-CoV-2 seroprevalence studies from 1 January 2020 to 30 March 2021.

Fig. 2

Estimated SARS-CoV-2 seroprevalences in the general human population in different countries using the geographic information system (GIS).

Fig. 3

Ecological random effects meta-regression analyses of SARS-CoV-2 seroprevalence in the general population in relation to: (A) a country's income level (a statistically significant downward trend in seroprevalence in countries with higher income levels). (B) Human development index (HDI) (a statistically significant downward trend in seroprevalence in higher HDI countries).

Fig. 4

Random effects meta-regression analysis of SARS-CoV-2 seroprevalence in the general human population in relation to time, showing the significant, upward trend in seroprevalence from the beginning of a COVID-19 epidemic to the first (A) and to the last (B) day of sampling (i.e. serum collection).