COVID-19 Serosurveys and Vaccine Study Site Preparations

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications & trials

Abstract

In July 2020, we commenced a community COVID-19 seroprevalence study at existing clinical trials sites in Mali. This study is a Public Health Surveillance Activity in collaboration with the Ministry of Health in Mali to describe the sero-epidemiology of COVID-19 in urban and rural populations. Using the demographic and clinical information collected from participants, we will describe the age-stratified seroprevalence and fraction of asymptomatic/pauci-symptomatic cases to help understand the penetration of SARS-CoV-2 into the community. Additional exploratory objectives to understand viral carriage, locally circulating variants, and improve direct virus detection at study sites have been added to help enhance local capacity for Public Health surveillance and possible future clinical trials. Separately, we have leveraged our in-house vaccine platforms to develop COVID-19 vaccine candidates that may be suitable for use in low/middle income countries like Mali. We report progress from the following publication in FY2025: Scaria PV, Rowe CG, Kosik I, Hu Z, Renn JP, Alani N, Kemanli P, Orr-Gonzalez S, Lambert LE, Adeyemi K, Doritchamou JYA, Barnafo EK, Rausch KM, Muslinkina L, Morrison RD, Todd JP, Esposito D, Lees A, Yewdell J, Duffy PE. SARS-CoV-2 receptor binding domain (RBD) protein-protein conjugate induces similar or better antibody responses as Spike mRNA in rhesus macaques. 2025. Vaccines. Jun 17;13(6):648. doi: 10.3390/vaccines13060648. Most early COVID-19 vaccines used SARS-CoV-2 Spike protein as the target antigen, but subsequent studies reported that Receptor Binding Domain (RBD) of Spike also can yield efficacious vaccines. We previously demonstrated that chemical conjugation of RBD to a carrier protein, EcoCRM®, enhanced antibody responses and induced strong virus neutralization activity in mice. In this publication, we compared the immunogenicity of this conjugate to that of an approved mRNA vaccine from Pfizer/BioNTech in rhesus macaques over a period of nine months. AS01-adjuvanted RBD conjugate induced a similar or better antibody response, receptor binding inhibition, and virus neutralization activity against different variants of SARS-CoV-2, compared to mRNA. IgG subclass profiles induced by conjugate and mRNA vaccines were initially dominated by IgG1 and IgG3 then switched to IgG2 and IgG4 dominant profiles during the subsequent six-month period. Polyclonal immune sera from the conjugate and mRNA had similar antibody avidity at multiple time points. In summary, antibody responses in rhesus macaques induced by the RBD-EcoCRM conjugate and the Spike mRNA vaccine are very similar. These results demonstrate the potential for the RBD-EcoCRM conjugate as a vaccine against SARS-CoV-2. From unpublished work: We surveyed longitudinal population seroprevalence activity, and observed sustained high seropositivity rates and evidence of protective neutralizing immunity, despite low vaccination rates in Malian communities. We demonstrated the natural progression of the COVID-19 pandemic in Malian communities, including population-wide exposure, stabilization of illness rates, and development of natural immunity suggestive of a rapid progression to endemicity. This work has been drafted as a manuscript nearing submission.