How so? Dryvax is pretty much the same as it was back then, and the diluted form is what they are planning for mass inoculations.
Dryvax is from the same strain of vaccinia used by the New York Board of Health in the 1870s. The method of growing the virus in calves dates to the 19th century. Prior to the 1870s the virus was passed from person to person. The Germans in the 1960s developed an attenuated strain that is incapable of infecting human cells, but produces a strong immune response. See the links in my prior post.