The development of a vaccine that brings schistosomiasis under immunological control has been the goal of many investigators all over the world for decades. This study was designed to test the effect of NHN vaccine which contains chemically modified Biomphalaria alexandrina Snail antigen on reducing the worm burden, inducing body immune response through raising the IgG titre and on reducing the incidence of pathological changes in organs of mice vaccinated then infected compared to mice infected without vaccination (prophylactic effect). Statistical analysis of the results showed that NHN dose-dependently raised the IgG titre in the vaccinated mice. The number of worms recovere from mice pre-injected with the vaccine then challenged with schistosome cercariae was about 10% of the number recovered from mice challenged without pre-vaccination. Vaccination with NHN significantly reduced the incidence of pathological changes in livers and intestines in challenged mice. These results suggest a possible potent effect of the compound tested (NHN vaccine) in preventing and even curing the pathological consequences of schistosomiasis infection