To provide a new low toxic adjuvant for latent application to human being.

A composition used for reinforcing immune responses in animals is prepared by a method for comprising (a) a process for preparing a chitosan solution, (b) a process for preparing a sodium hydroxide solution, (c) a process for preparing an oil/surfactant solution, wherein the oil can metabolically be degraded, and (d) a process for mixing the chitosan solution with the sodium hydroxide solution, the oil/surfactant solution, and an antigen to form an emulsion. The composition can be administered to an animal through an administration route making it possible to impart the immune response against the antigen to the animal.