**6. Conclusion**

A high interest in the development of vaccines against pathogenic *E. coli* occurred in recent years. This interest is related both to pathotypes affecting human and animal health. Few vaccines have been licensed and reached market and public health status. There is an intrinsic difficulty in directing the immune response to a bacterial species that is commonly part of the animal microbiota. The state of the art consists in identifying antigenic components that are exclusive of pathogenic subtypes.

In spite of these difficulties, science has gained a relevant knowledge of virulence, pathogenicity, genomics, and epidemiology of pathogenic *E. coli,* and with no doubt this will benefit vaccinology concerning pathogenic *E. coli*.
