SARS-CoV-2 seroprevalence in pregnant women during the first three COVID-19 waves in The Gambia

Abstract

AbstractObjectivesSARS-CoV-2 transmission in Sub-Saharan Africa has probably been underestimated. Population-based seroprevalence studies are needed to determine the extent of transmission in the continent.MethodsBlood samples from a cohort of Gambian pregnant women were tested for SARS-CoV-2 total IgM/IgG before (Pre-pandemic1:October-December 2019 andPre-pandemic2:February-June 2020) and during the pandemic (Post-wave1: October-December 2020,Post-wave2:May-June 2021; andPost-wave3: October-December 2021). Samples positive for total SARS-CoV-2 IgM/IgG were tested for protein-specific antibodies.ResultsSARS-CoV-2 total IgM/IgG seroprevalence was 0.9% 95%CI (0.2, 4.9) inPre-pandemic1; 4.1% (1.4, 11.4) inPre-pandemic2; 31.1% (25.2, 37.7) inPost-wave1; 62.5% (55.8, 68.8) inPost-wave2and 90.0% (85.1, 93.5) inPost-wave3.S-protein IgG and NCP-protein IgG seroprevalence also increased at eachPost-waveperiod. Although S-protein IgG and NCP-protein IgG seroprevalence was similar atPost-wave1, S-protein IgG seroprevalence was higher atPost-wave2andPost-wave3, [prevalence difference (PD) 13.5 (0.1, 26.8) and prevalence ratio (PR) 1.5 (1.0, 2.3) inPost-wave2; and 22.9 (9.2, 36.6) and 1.4 (1.1, 1.8) inPost-wave3respectively, p<0.001].ConclusionSARS-CoV-2 transmission in The Gambia during the first three COVID-19 waves was high, differing significantly from official numbers of COVID-19 cases reported. Our findings are important for policy makers in managing the near-endemic COVID-19.HighlightsHigh specificity of the IgM/IgG SARS-CoV-2 test using samples collected prepandemicVery high (>90%) SARS-CoV-2 seroprevalence after third COVID-19 wave in The GambiaHigh SARS-CoV-2 transmission contrasts with low number of COVID-19 reported cases