Human anthelminthic vaccines: Rationale and challenges

Helminth infections are the most common afflictions of humankind, affecting almost every single person living in profound poverty. Through mass drug administration (MDA) we have seen sharp declines in the global prevalence of some helminth infections, including lymphatic filariasis, onchocerciasis, and ascariasis. However, since 1990, there has been no appreciable decrease in the global prevalence of hookworm infection, schistosomiasis, or food-borne trematodiases. Through the activities of a non-profit product development partnerships and two research institutes, a total of five human anthelmintic vaccines for hookworm infection (two) and schistosomiasis (three) have advanced from discovery through manufacture and are now in Phase 1 clinical testing. At least three additional antigens, including two for onchocerciasis and one for schistosomiasis, are also advancing through preclinical development with the intention of moving into the clinic soon. These preventive human anthelmintic vaccines could be used as stand-alone technologies administered to infants as part of the Expanded Program on Immunization (EPI), or together with anthelmintic drugs in programs linked to MDA. Significant hurdles though could hinder the advancement of these vaccines into later-stage clinical and product development and licensure. They include the absence of a major pharma partner (and the resultant access to adjuvants and industrial scale manufacturing expertise), an uncharted roadmap for how to introduce anthelmintic vaccines into appropriate health systems, uncertain global access and regulatory strategies that might need to rely on developing country vaccine manufacturers and national regulatory authorities, and the lack of innovative financing schemes. However, the public health and economic benefits of introducing these vaccines could be massive and therefore deserve international attention and support.