Word: virus
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Dates: during 1960-1969
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...Death of a Virus...
...order to properly appraise the value of the two vaccines, one should examine their differences. Both are made from live polio viruses, cultured in test tubes on monkey kidney tissue. In the Salk process, the viruses are heated in formalin, killing them and making them safe for injection into the human blood stream. Fourteen days after the first shot, antibodies appear in the blood, giving a slight amount of protection against all three types of polio virus. Then a booster shot is administered and seven months later another booster, both raising the antibody level. A year later a fourth injection...
Sabin vaccine is made from "attenuated" live virus, virus which has been bred from selected strains of weak virus. The question has been raised as to the possibility that the weakened virus might mutate back to its wild, virulent state, regaining its deadly ability to attack the human nervous system. It is this question that forced Sabin to prolong his field tests, but today it seems clear that his strains are genetically stable and therefore safe, as now proven in over 140 million vaccinated persons...
...Sabin live virus is taken orally, mixed with a syrup, on a sugar cube, or in a bonbon. Within one day it multiplies in the intestines, preventing the entry of the natural virus and protecting against non-paralytic polio, neither of which the Salk vaccine can do. Although one does of oral vaccine immunizes indefinitely against any one type of virus, three doses are needed for Types I, II, and III. The live virus, while too weak to attack the nerve tissue or produce symptoms of disease, causes the human host to produce the necessary antibodies. Furthermore, the virus retains...
While many doctors will continue to apply dead virus shots, the PHS noted that, despite the Salk campaign,...outbreaks and even some severe epidemics still occur.... [even] among individuals who have had 3 or 4 doses of the vaccine." Thus, even in the United States, the final end of polio may come only with the use of oral vaccine...