SARS-CoV-2 seroprevalence and associated risk factors in periurban Zambia: a population-based study

Background: We nested a seroprevalence survey within the TREATS (Tuberculosis Reduction through Expanded Antiretroviral Treatment and Screening) project. We aimed to measure the seroprevalence of SARS-CoV-2 infection and investigate associated risk factors in one community (population similar to 27,00 0) with high prevalence of TB/HIV in Zambia. Methods: The study design was cross-sectional. A random sample of 3592 individuals aged >= 15 years enrolled in the TREATS TB-prevalence survey were selected for antibody testing. Randomly selected blocks of residence were visited between October 2020 and March 2021. Antibodies against SARS-CoV-2 were detected using Abbott-ARCHITECT SARS-CoV-2 IgG assay. Results: A total of 3035/3526 (86.1%) individuals had a blood sample taken. Antibody testing results were available for 2917/3035 (96.1%) participants. Overall, 401/2977 (13.5%) individuals tested positive for IgG antibodies. Seroprevalence was similar by sex (12.7% men vs 14.0% women) and was lowest in the youngest age group 15-19 years (9.7%) and similar in ages 20 years and older (similar to 15%). We found no evidence of an association between seroprevalence and HIV-status or TB. There was strong evidence (p<0.001) of variation by time of enrollment, with prevalence varying from 2.8% (95% CI 0.8-4.9) among those recruited in December 2020 to 33.7% (95% CI 27.7-39.7) among those recruited in mid-February 2021. Conclusion: Seroprevalence was 13.5% but there was substantial variation over time, with a sharp increase to approximately 35% toward the end of the second epidemic wave. (C) 2022 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.