Methods employed in a 2021 population-based serosurvey in Somalia

This paper describes the design and methods of a serosurvey conducted in Somalia in 2021. The study had several concurrent aims: a) to estimate seroprevalence of antibodies to SARS-CoV-2, b) to obtain age-specific data on susceptibility to poliovirus, measles, rubella, diphtheria, and tetanus; and c) to estimate seroprevalence of pathogens causing malaria and neglected tropical diseases. Participants were recruited from persons seeking care at government health facilities as well as friends and family members who accompanied those seeking care. Respondents answered interview questions to establish their demographic profile, their COVID-19 exposure and experience, and, for children, their routine immunization status. Each participant contributed a sample of blood for serum or dried blood spots. Serum samples were analyzed in Somalia for SARS-CoV-2 and dried blood spots were analyzed at the US Centers for Disease Control and Prevention (US CDC) for the other diseases and antigens of interest. This manuscript describes the study design, logistics, laboratory methods, and data management steps used to compile the study dataset. Study results will be reported in a series of manuscripts to follow.