Vaccines against prion disease eliciting a humoral immune response when administered mucosally are described. The vaccines comprise a prion protein, a prion protein fragment, or a non-amyloidogenic prion protein homolog and an adjuvant suitable for inducing a humoral immune response after mucosal administration. Suitable adjuvants include cholera toxin subunit B, heat-labile enterotoxin and aluminum hydroxide. Alternatively, the vaccine comprises a vector encoding a prion protein, fragment, or homolog in an attenuated Salmonella host. The vaccines can be used to prevent or treat prion disease in humans and other mammals.