ABSTRACT
Background: As part of an international multi-country study on COVID-19 vaccine immunogenicity (InVITE, NCT05096091), we sought to characterize baseline anti-Nucleocapsid (N) and anti-Spike (S) seropositivity by country and by self-report of prior positive SARS-CoV-2 test result. Method(s): 3063 vaccine-naive individuals from the InVITE study cohort, who received a COVID-19 vaccine as part of their country's national immunization programs at participating sites in Democratic Republic of Congo (DRC), Guinea, Liberia and Mali, were enrolled between August 2021 and February 2022. Demographic and baseline characteristics were collected at study enrollment. Blood was collected at baseline prior to initiation of the vaccine regimen. SARS-CoV-2 anti-S antibody and anti-N antibody levels were measured using Quanterix anti-S IgG semi-quantitative antibody and BioRad Platelia SARSCoV- 2 anti-N Total Ab assays, respectively. Demographic characteristics were assessed for association with positive anti-S and anti-N serology. Result(s): Baseline demographics and serology results by country and overall are shown in the table. Conclusion(s): Despite low numbers of prior self-reported positive SARS-CoV-2 test, the serology results in this cohort indicate prior infection in a significant proportion of the InVITE study participants prior to receipt of a first dose of COVID-19 vaccination. These results suggest widespread previous SARS-CoV-2 infections that were unrecognized possibly due to mild-no symptoms, poor access to/availability of testing and/or limited monitoring through surveillance. Baseline Demographics and Serology Results.