The comic refers to developing smallpox vaccine, but smallpox vaccine was first made from the less virulent cowpox vaccine, which would require a less virulent zombie virus, and the story never explains how that could have happened. Note that there are other ways to develop a vaccine, and the first one, smallpox, was developed in 1796. Also, inoculations by taking scabs and pus and scratching skin with it was done in the 17th century and earlier. Dangerous, but obviously some decided to take the risk. Thanks for the translations!!!
@Ced1106 I think she was only making a comparison of how crude the vaccine itself was, not drawing parallels to the process for the smallpox vaccine.
(It's implied that she may have caused the outbreak/developed the virus to begin with. Since it was purely curiosity, we have no way of knowing what she was curious about/whether she had previously used some similar version on herself.)