BALB/c and NIH mice have been successfully vaccinated against the intestinal nematode Trichinella spiralis by oral administration of crude larval extracts (CLE) and excretory-secretory (ES) products derived from first stage T. spiralis larvae (L1) encapsulated in microcapsules made of copolymers of the metacrylic acid (Eudragit L100). Oral vaccination stimulated the secretion of IFN-gamma and inhibited the secretion of IL-4 in spleen and mesenteric lymph nodes (MLN) of BALB/c mice. In vaccinated mice the proportion of CD4+ cells increased (p<0.05) in Peyer's patches (PP) and decreased (p<0.05) in spleen whereas the proportion of CD19+ cells decreased (p<0.05) in both PP and spleen, with regard to unvaccinated controls. No variation was evident for the proportion of CD8+ cells. Oral vaccination elevated the antigen-specific serum IgG1 and IgA (p<0.05) as well as the antigen-specific IgA response in MLN (p<0.05). It is concluded that this way of vaccination induced a concurrent Th1/ Th2 local and systemic responses that are protective and at the same time they may help balancing the strong Th2 response triggered by helminth infections.