Post-pandemic molecular and serologic detection of SARS-CoV-2 among vaccinated and unvaccinated participants in Yenagoa, Bayelsa State, Nigeria

Post-pandemic monitoring of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is essential to evaluate the long-term outcome of coronavirus disease 2019 (COVID-19) vaccination and natural immunity through infection. A cross-sectional study was conducted among 200 participants, comprising 100 vaccinated and 100 unvaccinated persons among different age groups and gender in Bayelsa State, Nigeria. Saliva, blood, oropharyngeal and nasopharyngeal swab samples were collected from the participants and were analysed using standard serologic (Rapid Diagnostic Antibody Test kit) and molecular methods (RT-qPCR). The study used descriptive statistical analysis and chi-square test to assess the relationship between serostatus, vaccination status, age, and gender. The molecular results showed an overall infection rate of 7.5%, which was significantly fewer (p < 0.05) in vaccinated individuals (4.0%) testing positive for SARS-CoV-2 compared to unvaccinated individuals (11.0%). The result of serological analysis revealed a high overall SARS-CoV-2 antibody seropositivity rate of 95.5%, with 98% among vaccinated individuals, which was significantly different (p < 0.05) from the 93% among unvaccinated individuals. No significant association was found between seropositivity and either age or gender (p > 0.05). However, seropositivity was slightly higher among males in both vaccinated and unvaccinated groups. The study established a high SARS-CoV-2 antibody seroprevalence among vaccinated and unvaccinated individuals in Bayelsa State.