Encouraging results have been obtained in phase I studies in Burkina Faso and Mali. In the former, ProC6C was found to be safe and well-tolerated in adults, and elicited the highest levels of antibodies when combined with Matrix-M. The vaccine generated antibodies against both the sporozoite and gametocyte stages.
The PfTBV project has also established a platform for evaluating innovative transmission-blocking malaria vaccines. Following the positive phase I results, a phase II human challenge study has begun in Mali, through which healthy adult volunteers will be vaccinated with ProC6C and then challenged with malaria parasites under carefully controlled conditions to determine how well the vaccine prevents parasite multiplication.
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A new malaria vaccine shows the promising ability both to prevent infection and to block transmission of the malaria parasite.
The two licensed malaria vaccines, RTS,S/AS01 and R21/Matrix-M, represent a major step forward in malaria control. However, they are of modest efficacy and do not have any impact on gametocytes, the form of the malaria parasite that is taken up when mosquitoes bite, developing within the mosquito into the stage that initiates new infections. Additional vaccines, including those that can block transmission of malaria parasites, are thus still greatly needed.
One particularly interesting candidate is ProC6C, a multi-component vaccine designed to act on multiple stages of parasite development. As well as preventing disease, it also has the potential to block transmission by acting against the gametocyte stage. ProC6C is being developed as part of the EDCTP-funded PfTBV project, which has been developing transmission-blocking malaria vaccines and creating an infrastructure for their evaluation in endemic countries. The consortium is led from Mali and includes the vaccine’s developers, the Statens Serum Institut (SSI) in Denmark.
ProC6C includes multiple antigens, including circumsporozoite protein (CSP), a common vaccine target, and novel antigens (Pfs48/45 and Pfs230). It has been combined with a powerful adjuvant, Matrix-M, which has also been combined with R21.
A vaccine to prevent malaria transmission