2.1. Scientific challenges
Currently there are no licensed anthelminthic vaccines for humans. Two experimental schistosomiasis vaccines are undergoing early stage clinical testing in Brazil and sub-Saharan Africa [19] and [20], while the Human Hookworm Vaccine is the only vaccine in clinical development for hookworm infection. Hookworms are complex multicellular parasites, so that producing an efficacious vaccine against this helminth is in some respects an even more formidable challenge than producing vaccines against unicellular parasites such as those that cause malaria and other protozoan infections. The feasibility of producing an efficacious vaccine against hookworm has been reviewed previously and is based on past successes in developing an effective irradiated larval canine hookworm vaccine and in demonstrating the efficacy of recombinant protein vaccines in laboratory animal-challenge studies [9] and [21].