Seroprevalence of endemic and emergent coronaviruses among SARS-COV-2 patients and healthcare workers in Abidjan, Côte d’Ivoire

Understanding the serological landscape of endemic and emergent coronaviruses is critical to interpreting early-pandemic immune responses and evaluating hypotheses of cross-reactivity. It was proposed that prior exposure to endemic coronaviruses could affect susceptibility or shape symptom severity through cross-reactive antibody responses. However, little was known about baseline coronavirus seroprevalence in many global regions, including Abidjan, Côte d’Ivoire. Characterizing this landscape provides key insights into early pandemic immunity and the potential influence of prior coronavirus exposures on SARS-CoV-2 immune response. Here, we probe this using data from syndromic surveillance in Abidjan, Côte d’Ivoire, collected between September 2020 and July 2021. We quantified IgG antibody levels to both spike and nucleocapsid proteins for emergent coronaviruses (SARS-CoV-1, SARS-CoV-2, and MERS-CoV) and endemic coronaviruses (HKU1, OC43, NL63 and 229E) using high-throughput multiplex bead assay. Samples were collected from SARS-CoV-2 negative healthcare workers (N = 202) and SARS-CoV-2 positive patients (N = 207). SARS-CoV-2 positive patients returned for repeat sampling at day 28 (N = 131). SARS-CoV-2 negative healthcare workers had higher SARS-CoV-1 seropositivity [0.27 (CI: 0.21–0.33) vs. 0.18 (CI: 0.13–0.24)] and SARS-CoV-2 seropositivity [0.52 (CI: 0.46–0.59) vs. 0.37 (CI: 0.31–0.44)] than SARS-CoV-2 positive patients. There were no significant differences among endemic coronaviruses between the healthcare workers and patients. Among the endemic coronaviruses, seropositivity was highest for 229E at 0.96 (95% CI: 0.94–0.98) and lowest for HKU1 at 0.56 (95% CI: 0.51–0.61) We found no significant sex difference in seropositivity to any coronavirus. These findings provide a snapshot of endemic and emergent coronavirus seroprevalences during the beginning of the COVID-19 pandemic in Abidjan. We observed high seroprevalence to endemic alphacoronaviruses (229E and NL63), slightly lower levels for betacoronaviruses (HKU1 and OC43), and cross-reactive antibody signals to SARS-CoV-1. Among SARS-CoV-2 positive patients sampled again after 28 days, we did not observe evidence of boosting antibody levels to endemic coronaviruses, suggesting no cross-reactive responses. However, studies incorporating conserved S2 regions are needed to more fully assess cross-reactivity.