SARS-CoV-2 seroprevalence in vaccine-naïve participants from the Democratic Republic of Congo, Guinea, Liberia, and Mali

Abstract

Objectives: The InVITE study, starting in August 2021, was designed to examine the immunogenicity of different vaccine regimens in several countries including the Democratic Republic of Congo, Guinea, Liberia, and Mali. Prevaccination baseline samples were used to obtain estimates of previous SARS-CoV-2 infection in the study population.

Methods: Adult participants were enrolled upon receipt of their initial COVID-19 vaccine from August 2021 to June 2022. Demographic and comorbidity data were collected at the time of baseline sample collection. SARS-CoV-2 serum anti-Spike and anti-Nucleocapsid antibody levels were measured.

Results: Samples tested included 1016, 375, 663, and 776, from DRC, Guinea, Liberia, and Mali, respectively. Only 0.8% of participants reported a prior positive SARS-CoV-2 test, while 83% and 68% had anti-Spike and anti-Nucleocapsid antibodies, respectively.

Conclusions: Overall SARS-CoV-2 seroprevalence was 86% over the accrual period, suggesting a high prevalence of SARS-CoV-2 infection. Low rates of prior positive test results may be explained by asymptomatic infections, limited access to SARS-CoV-2 test kits and health care, and inadequate surveillance. These seroprevalence rates are from a convenience sample and may not be representative of the population in general, underscoring the need for timely, well-conducted surveillance as part of global pandemic preparedness.

Keywords: COVID-19; InVITE; SARS-CoV-2; Seroprevalence; Vaccines; West Africa.

Figure 1:. Cumulative accrual by country

Cumulative accrual from the time of study initiation until the enrollment target was reached. The lines represent accrual for each country.

Figure 2:. Baseline anti-S and anti-N antibody levels

(A) Distribution of levels and proportion positive (95% CI) for the anti-Spike serology assay; dotted line represents the 770 ng/mL positivity threshold. (B) Specimen ratio distribution and proportion positive (95% CI) for the anti-Nucleocapsid serology assay; dotted line represents the ratio >1 positivity threshold. For figures A and B, the line in the box represents the median, the lower and upper box lines correspond to the first and third quartiles, and the lines extending above and below the box represent 1.5 IQR. (C) Concordance of anti-Nucleocapsid and anti-Spike antibody positivity, with Spearman rank correlation. Concordant samples are blue; non-concordant samples are red.