Bacterial vaccines: old and new, veterinary and medical.

Developments in veterinary and medical bacterial vaccines are outlined. In the former case, economic considerations are paramount, and cruder, less purified products of proven efficacy continue to be employed. For human use, however, safety and absence of side effects are increasingly demanded. Various examples of human and veterinary vaccines are discussed, and interaction between the two fields is illustrated by reference to the pig-bel disease in New Guinea and the possible aetiology of Sudden Infant Death Syndrome.