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.