Pox diseases, caused either by smallpox virus or zoonotic pox viruses or animals, continue to be of potential danger to a non-vaccinated population. Mass vaccinations will become necessary and will then also be administered to persons with immunological aberrations. The vaccines which are presently used against smallpox cause severe complications in such hosts. In contrast, the attenuated vaccinia virus strain MVA is safe even under the conditions of immunosuppression and is recommended for the production of smallpox vaccines. Because of the special epizootic situations and the numerous immunosuppressive factors present in developing countries, the use of such a safe pox vaccine there is of crucial importance.