The present invention provides a method of treatment or prophylaxis of enteric disease caused by Gram negative bacteria. The method includes the step of administering a vaccine or a hyperimmune material raised against said vaccine to an individual. The vaccine comprises one or more cell wall antigens reactive in a manner characteristic of O group serotypes, or reactive in a manner characteristic of lipopolysaccharide associated antigens, and at least some of said antigens are separated from bacterial cell walls or wall fragments. The invention also provides composition containing hyperimmune material as well as uses of the composition and vaccine.
