Global SARS-CoV-2 seroprevalence: a systematic review and meta-analysis of standardized population-based studies from Jan 2020-May 2022

Abstract

BackgroundCOVID-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/MethodsWe 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.ResultsWe 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.ConclusionsGlobal 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.

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

“…We observed lower seroprevalence in children 0-9, perhaps attributable to milder infections in this group which are associated with lower antibody titres [47] and school closures which have been common and lengthy in some African countries. [48] In contrast to our global analysis,[9] we did not find lower seroprevalence in adults 60+ years compared to adults 20-29 years. These results may be due to increased intergenerational mixing at the household level, as prior research in Africa has shown that households sharing space with persons ages 60+ may have increased transmission risk [44].…”

“…[48] In contrast to our global analysis, [9] we did not find lower seroprevalence in adults 60+ years compared to adults 20-29 years. These results may be due to increased intergenerational mixing at the household level, as prior research in Africa has shown that households sharing space with persons ages 60+ may have increased transmission risk [44].…”

“…The pooled seroprevalence in Africa estimated in this study (65.1% in Q3 2021) is among the highest in the world (comparable to the South-East Asia region). [9] With vaccination coverage in Africa being low during the study period (4.8% in September 2021), [6] this is mostly driven by infections. [42,43] The exact role of cross-reactivity on seroprevalence estimates warrant further investigation.…”

“…[8] These studies provide us with the opportunity to understand SARS-CoV-2 epidemiology in Africa despite low vaccination coverage and case under-ascertainment. To note, our investigative team has also conducted an analysis of SEROPREV studies globally, including regional comparison, which serves as the foundational source for the methods and analyses further developed in this paper [9] to provide more detailed analyses for Africa.…”

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

“…20 Finally, global synthesis and comparison initiatives: where this has been carried out for seroprevalence, these delays have caused limitations in the synthesis that can be done. 3…”