Population seroprevalence of SARS-CoV-2 antibodies in Anambra State, South-East, Nigeria

OBJECTIVE: The objective of this study was to determine the proportion of the Anambra State population that had been infected by the SARS-CoV-2 virus and developed antibodies before the second wave. METHODS: The WHO-recommended health facility-based cross-sectional approach was adapted for this survey. Between 8(th) and 15(th) December 2020, 3142 participants across the 21 local government areas (LGAs) of the State, aged one year and over, attending randomly selected health facilities, were recruited. Demographic and symptom-related information were collected from the participants as well as whole peripheral blood, which was tested for SARS-CoV-2 IgG and IgM with rapid test kits. RESULTS: 425 participants tested positive for IgG only, 74 for IgM only, while 54 were positive for both IgG and IgM. Overall, 553 positives were recorded, giving a crude seroprevalence of 17(.)6% (95% CI = 16(.)26 – 18(.)98). It ranged widely from 31(.)9% (95% CI = 24(.)43 – 40(.)22) in Onitsha North LGA to 5(.)4% (95% CI = 2(.)19 – 10(.)78) in Awka north. Bayesian Adjustments yielded a state seroprevalence of 16(.)1%. CONCLUSION: One in six state residents had been infected by SARS-CoV-2 and developed antibodies before the second wave. All LGAs, age groups, sexes, and settlement types were affected by COVID-19. A large proportion of the population remained susceptible to SARS-CoV-2.