Periodic Reporting for period 2 - VASA (Vaccine Against Schistosomiasis for Africa. A Phase I clinical study of the SchistoShield® anti-schistosomiasis vaccine in adults in endemic areas of sub-Saharan Africa)
Reporting period: 2021-08-01 to 2022-12-31
The mainstay of schistosomiasis control is preventative and therapeutic administration of the anthelminthic praziquantel (PZQ). However, repeated treatment is needed for curative parasite clearance. A single infection does not prevent future infection; as such, the cost-effectiveness of mass-treatment programs is compromised when reinfection is common. In order to combat the schistosomiasis burden, large-scale prevention strategies, such as mass vaccination campaigns, that complement treatment programs, are necessary. According to the WHO, target groups for large-scale, periodic treatment include school-aged children and adults at high risk (e.g. fishermen, farmers, irrigation workers and other persons who have increased contact with infested water) or entire communities living in highly endemic areas. Periodic PZQ treatment has shown to reduce clinical symptoms; however, there remains a gap between those who require and those who receive treatment. According to a 2015 estimate, only 28.2% of overall cases requiring treatment actually received care. An alternative or supplementary control method is the reduction of intermediate snail hosts using molluscicides, but this is even more challenging and costly6 since frequent application of molluscicides is necessary and logistically challenging. Therefore, an efficacious and safe vaccine, giving long-lasting protection against all forms of schistosomiasis, will have a profound impact on infection control. In fact, “Science” ranked a schistosomiasis-vaccine among the top-10 most urgently needed vaccines. SchistoShield® (Sm-p80 plus GLA-SE) is one of the most promising vaccine candidates with documented efficacy against all major schistosome species studied in rodents and nonhuman primate studies.
The major objectives of the VASA project are to:
1. Assess the safety/immunogenicity of SchistoShield® in a Phase I clinical study in healthy adults from Africa;
2. Refine and develop a female worm schistosome human challenge model
3. To identify correlates of protection, innate and adaptive immune signatures, gene expression and the role of antibodies in the prevention/control of Schistosoma infections;
4. Foster a global consortium to advance research on schistosomiasis disease burden, vaccines and address downstream access constraints in resource-poor settings
During the 2nd project period, the VASA consortium made substantial progress towards achieving overall project objectives, disseminating research highlights, and generating valuable research data. With much of the foundational groundwork laid during the 1st project period, the 2nd project period began in August 2021 with four active studies—the controlled human infection study led by Leiden, the cost-of-illness study led by the International Vaccine Institute (IVI), the sero-epidemiology study in Burkina Faso led by the University of Ouagadougou, and the sero-epidemiology study in Madagascar led by the University of Antananarivo. Over the course of this project period, all four of these studies completed their planned study activities, marking the successful conclusion of these work packages. The timely achievement of these studies is a testament to the hard work and collaboration of the VASA partners, and the study results will be disseminated through peer-reviewed publications, scientific conferences, and more.
Other VASA studies were activated during this project period, namely the schistosomiasis vaccine cost-effectiveness analysis, led by the IVI, and the immune signatures identification study led by the Texas Tech University Health Sciences Center. These work packages carried out preparatory activities such as study protocol standardization and SOP development, and we expect to see further progress in the next project period.
VASA data collected is valuable for and relevant to:
• The acceleration of the schistosomiasis vaccine Sm-p80.
• Data from the human challenge model and non-human primate model of infection and disease will help identify immune markers and potential correlates of protection.
• Policymakers and opinion leaders of early adopter countries to identify data requirements for serious policy deliberations on the introduction of this vaccine into public health programs.
• Gavi and Ministries of Health as the cost-effectiveness data will be used to guide and support the introduction of schistosomiasis vaccines. The transferability of results and overall acceptance is a major component of VASA.
• Research groups interested in assessing the public health impact of Sm-p80-based schistosomiasis vaccine beyond the VASA program (e.g. reduction of resistance, complications and hospitalizations).
• Future vaccine manufacturers incl. DCVMs of Sm-p80-based vaccine as VASA will assess vaccine safety and effectiveness in the African setting.