[Experiences with immunization against orthopox viruses of humans and animals using vaccine strain MVA].

Immunizations against orthopox virus infections require a replicating, but safe vaccinia virus. The strain MVA is well suited concerning this matter. Human beings and animals can be vaccinated without any risk. The virus propagated in cell culture is non-virulent and lost its contagiosity. Multiplication in vaccinated men and animals is limited and excretion does not happen. As known for other attenuated virus strains, there must be a minimal effective virus concentration in the vaccine, which is 10(7.5) TCID50 per ml for MVA. To achieve a solid basic immunity which endures for a minimal of one year, two parenteral applications of MVA at intervals of at least 3 weeks are necessary.