Severe Acute Respiratory Syndrome Coronavirus-2 seropositivity in South-central Uganda, during 2019 - 2021

ABSTRACT

Globally, key subpopulations have a high risk of contracting SARS-CoV-2. In Uganda, limited access to personal protective equipment amidst lack of clarity on the extent of the community disease burden may exacerbate this situation. We assessed SARS-CoV-2 antibody seroprevalence among high-risk sub-populations, including healthcare workers, persons within the general population previously reporting experiencing key COVID-19 like symptoms and archived plasma specimens collected prior to confirmation of COVID-19 in Uganda. We collected venous blood from HCWs at selected health facilities and from population-cohort participants who reported specific COVID-19 like symptoms in a prior phone-based survey conducted during the first national lockdown (May-August 2020). Pre-lockdown plasma collected from individuals considered high risk for SARS-CoV-2 infection was retrieved. Specimens were tested for antibodies to SARS-CoV-2 using the CoronaChek rapid COVID-19 IgM/IgG lateral flow test assay. IgM only positive samples were confirmed using a chemiluminescent microparticle immunoassay (ARCHITECT AdviseDx SARS-CoV-2 IgM) which targets the spike. SARS-CoV-2 exposure was defined as either confirmed IgM, both IgM and IgG or sole IgG positivity. The seroprevalence of antibodies to SARS-CoV-2 in HCWs was 21.1% [95%CI 18.2-24.2]. Of the phone-based survey participants, 11.9% [95%CI 8.0-16.8] had antibodies to SARS-CoV-2. Among 636 pre-lockdown plasma specimens, 1.7% [95%CI 0.9-3.1] were reactive. Findings suggest a high seroprevalence of antibodies to SARS-CoV-2 among HCWs and substantial exposure in persons presenting with specific COVID-19 like symptoms in the general population of South-central Uganda. Based on current limitations in serological test confirmation, it remains unclear whether pre-lockdown seropositivity implies prior SARS-CoV-2 exposure in Uganda.