A study of variation in the number of pock lesions formed on the chorioallantoic membranes of chick embryos by titrating National Reference smallpox vaccine virus.
D000818:Animals; D002642:Chick Embryo / Q000382:microbiology; D008722:Methods; D012900:Smallpox Vaccine / Q000592:standards*; D014616:Vaccinia virus / Q000472:pathogenicity
D012900:Smallpox Vaccine