N. americanus ASP-2 (Na-ASP-2) was selected as the most promising vaccine candidate targeting the larval stage of hookworm infections. Dogs vaccinated with A. caninum irL3 produced a direct antibody response to the antigen ASP-2. Furthermore, high concentrations of IgG antibodies were observed after vaccination of dogs and hamsters with recombinant A. caninum or Ancylostoma ceylanicum ASP-2. There was an observed robust secondary immune response in these animals after infection with L3, producing low levels of adult hookworms, fecal counts and reduced blood loss. Anti-ASP-2 IgG collected from vaccinated animals prevented the movement of larval hookworms throughout tissue samples. Studies of regions where hookworm is endemic showed that anti-ASP-2 antibodies are correlated with reduced risk of hookworm infections.