Vaccinia virus was the first vaccine ever used, resulting after more than 200 years in the eradication of Smallpox, one of the most fatal diseases in history. The development of manipulation techniques for the virus genome has made it possible to contemplate new uses for this old vaccine. Among these, its use as a vehicle for the expression of genes from human or animal pathogens, to generate recombinant vaccines that combine the excellent characteristics of the vaccine vector with the expression of exogenous genes. In addition to its use as a vaccine, there are great expectations regarding the use of recombinant Vaccinia viruses as a biotechnological tool for protein expression or even in the treatment of tumors as an oncolytic agent.
In the field of vaccines, and due to current vaccine standards, it is necessary to increase the safety and immunogenicity of the new candidates with respect to those of the classic vaccine strains that were used against smallpox. One of the improved vectors is the Vaccinia strain called MVA, which was obtained by blind passages, but there are also other alternatives derived from a greater understanding of the functions of viral genes, which could allow obtaining vaccine vectors with optimized characteristics.
