High pre‐Delta and early‐Omicron SARS‐CoV‐2 seroprevalence detected in dried blood samples from Kinshasa (D.R. Congo)

Abstract

AbstractStudies on the impact of the COVID‐19 pandemic in sub‐Saharan Africa have yielded varying results, although authors universally agree the real burden surpasses reported cases. The primary objective of this study was to determine SARS‐CoV‐2 seroprevalence among patients attending Monkole Hospital in Kinshasa (D.R. Congo). The secondary objective was to evaluate the analytic performance of two chemiluminescence platforms: Elecsys® (Roche) and VirClia® (Vircell) on dried blood spot samples (DBS). The study population (N = 373) was recruited in two stages: a mid‐2021 blood donor cohort (15.5% women) and a mid‐2022 women cohort. Crude global seroprevalence was 61% (53.9%–67.8%) pre‐Delta in 2021 and 90.2% (84.7%–94.2%) post‐Omicron in 2022. Anti‐spike (S) antibody levels significantly increased from 53.1 (31.8–131.3) U/mL in 2021 to 436.5 (219.3–950.5) U/mL in 2022 and were significantly higher above 45 years old in the 2022 population. Both platforms showed good analytic performance on DBS samples: sensitivity was 96.8% for IgG (antiN/S) (93.9%–98.5%) and 96.0% (93.0%–98.0%) for anti‐S quantification. These results provide additional support for the notion that exposure to SARS‐CoV‐2 is more widespread than indicated by case‐based surveillance and will be able to guide the pandemic response and strategy moving forward. Likewise, this study contributes evidence to the reliability of DBS as a tool for serological testing and diagnosis in resource‐limited settings.