This invention describes a new vaccine against Strongyoides stercoralis, which establishes a parasitic infection that affects an estimated 100-200 million people worldwide. The potential for fatal disease associated with S. stercoralis infection and the difficulty in treating hyperinfection underscores the need for prophylactic vaccines against the disease. This vaccine uses S. stercoralis immunoreactive antigen (SsIR); a novel antigen capable of providing 70-90 % protection for mice immunized with the antigen. In addition, sera from immunized mice have also been used to effectively protect naive mice from infection.

The invention may also have potential use in diminishing allergic responses, as Strongyoides stercoralis infection has been shown to reduce the murine response to allergens. Consequently, SsIR may be used to immunize individuals and reduce the allergic response. The antigen may also be used to identify homologous antigens from other parasitic nematodes that may be important for vaccine development.