The second-generation vaccines are also administered through scarification with a bifurcated needle, and they carry the same side effects as the first-generation vaccinia strain that was cloned. However, the use of eggs or cell culture allows for vaccine production in a sterile environment, while first-generation vaccine contains skin bacteria from the animal that the vaccine was grown on.Ernest William Goodpasture, Alice Miles Woodruff, and G. John Buddingh grew vaccinia virus on the chorioallantoic membrane of chicken embryos in 1932. The Texas Department of Health began producing egg-based vaccine in 1939 and started using it in vaccination campaigns in 1948.: 588  Lederle Laboratories began selling its Avianized smallpox vaccine in the United States in 1959. Egg-based vaccine was also used widely in Brazil, New Zealand, and Sweden, and on a smaller scale in many other countries. Concerns about temperature stability and avian sarcoma leukosis virus prevented it from being used more widely during the eradication campaign, although no increase in leukemia was seen in Brazil and Sweden despite the presence of ASLV in the chickens. : 588 Vaccinia was first grown in cell culture in 1931 by Thomas Milton Rivers. The WHO funded work in the 1960s at the Dutch National Institute for Public Health and the Environment (RVIM) on growing the Lister/Elstree strain in rabbit kidney cells and tested it in 45,443 Indonesian children in 1973, with comparable results to the same strain of calf lymph vaccine.
Case 21 included several children and adults. Crucially all of at least four whom Jenner deliberately inoculated with smallpox virus resisted it. These included the first and last patients in a series of arm-to-arm transfers. He concluded that cowpox inoculation was a safe alternative to smallpox inoculation, but rashly claimed that the protective effect was lifelong. This last proved to be incorrect. Jenner also tried to distinguish between True cowpox which produced the desired result and Spurious cowpox which was ineffective and/or produced severe reaction. Modern research suggests Jenner was trying to distinguish between effects caused by what would now be recognised as non-infectious vaccine, a different virus (e.g. paravaccinia/milkers nodes), or contaminating bacterial pathogens. This caused confusion at the time, but would become important criteria in vaccine development. A further source of confusion was Jenners belief that fully effective vaccine obtained from cows originated in an equine disease, which he mistakenly referred to as grease. This was criticised at the time but vaccines derived from horsepox were soon introduced and later contributed to the complicated problem of the origin of vaccinia virus, the virus in present-day vaccine. : 165–78 The introduction of the vaccine to the New World took place in Trinity, Newfoundland, in 1798 by Dr. John Clinch, boyhood friend and medical colleague of Jenner. The first smallpox vaccine in the United States was administered in 1799. The physician Valentine Seaman gave his children a smallpox vaccination using a serum acquired from Jenner.