Smallpox is a virus with a fatality rate of about 30%, and those that survive the disease have terrible scarring and lingering problems. edward jenner is famous for a now notorious experiment in which he developed the first vaccine for smallpox. in the experiment jenner first exposed a small boy to cowpox, which is relatively harmless. the boy got cowpox and recovered. jenner then exposed the boy to smallpox by walking him through a hospital ward. the boy lived. which conclusion is not valid? a) cowpox virus can be used as a vaccine against smallpox. b) immunity to cowpox virus also grants immunity to smallpox. c) cowpox virus and smallpox virus are probably very similar. d) smallpox virus would be a good choice for a vaccine against cowpox.