Effect of vaccination on the clinical response, pathogenesis and transmission of mousepox

The effects of vaccination with the IHD-T strain of vaccinia virus on the course and severity of ectromelia virus infection was investigated in BALB/c mice. Protection from lethal mousepox occurred when mice were vaccinated and challenged on the same day and protection persisted for at least 9 months. Vaccinated mice were not protected from infection or from lesions, but necrotic lesions in vaccinated mice were usually mild and were accompanied by inflammation, whereas necrosis in unvaccinated mice was severe and not accompanied by inflammation. Inoculated feet of previously vaccinated mice contained infectious ectromelia virus for at least 28 days. Vaccinated-challenged mice transmitted infection to non-immune cagemates for up to 2 weeks, but only rarely transmitted virus to vaccinated cagemates. These results emphasize that vaccination protects mice against lethal mousepox, but it does not prevent infection. In addition, vaccination reduces, but does not eliminate, transmission of infection to non-immune and immune mice.