Longitudinal Profile of Antibody Response to SARS-CoV-2 in Patients with COVID-19 in a Setting from Sub–Saharan Africa: A Prospective Longitudinal Study

Abstract

Background: Serological testing for SARS-CoV-2 plays an important role for epidemiological studies, in aiding the diagnosis of COVID-19, and assess vaccine responses. Little is known on dynamics of SARS-CoV-2 serology in African settings. Here, we aimed to characterize the longitudinal antibody response profile to SARS-CoV-2 in Ethiopia. \n \nMethods: In this prospective study, a total of 102 PCR-confirmed COVID-19 patients were enrolled. We obtained 802 plasma samples collected serially. SARS-CoV-2 antibodies were determined using four lateral flow immune-assays (LFIAs), and an electrochemiluminescent immunoassay. We determined the sensitivity, specificity, as well as seroconversion dynamics. \n \nFindings: Serological positivity rate ranged between 12%-91%, depending on timing after symptom onset. There was no difference in positivity rate between severe and non-severe COVID-19 cases. The specificity ranged between 90%-99%. Agreement between different assays ranged between 84%-92%. Overall, 28/102 (27.5%) seroconverted by one or more assays tested, within a median time of 11 (IQR: 9–15) days post symptom onset. The median seroconversion time among symptomatic cases tended to be shorter when compared to asymptomatic patients [9 (IQR: 6–11) vs. 15 (IQR: 13–21) days; p=0.002]. Overall, seroconversion reached 100% 5.5 weeks after the onset of symptoms. Notably, 10 (9.8%) patients failed to mount a detectable antibody response by any of the assays tested during of follow-up. \n \nInterpretation: Longitudinal assessment of antibody response in African COVID-19 patients revealed heterogeneous responses. This underscores the need for a comprehensive evaluation of seroassays before implementation. Factors associated with failure to seroconvert needs further research. \n \nFunding: The European and Developing Countries Clinical Trial Partnership (EDCTP) – European Union. \n \nDeclaration of Interest: DW is European and Developing Countries Clinical Trials Partnership (EDCTP) Senior Research Fellow, and received funding for EvaLAMP project on Leishmaniasis Diagnostics; he serves as Strategic and Scientific Advisory Board of the Research Networks for Health Innovations in Sub-Saharan Africa (German Federal Ministry of Education and Research), and has received an honorarium for lectures and presentations from the Ethiopian Ministry of Science and Higher Education. TRW is employee of PharmAccess Foundation, is Board Member of Mondial Diagnostics, and Advisory Board member of Healthinc, The Netherlands. All other authors have no declarations to disclose. \n \nEthical Approval: The study protocol was reviewed and approved by the Health Research Ethics Review Committee of Mekelle University College of Health Sciences (#ERC 1769/2020).