Vaccines against diseases caused by viruses have traditionally been made from animals. This has often proved a dangerous approach as contaminants from animal tissues have produced fatal results in people. For instance, in 1967 a previously unknown virus - the Marburg agent - killed 7 people handling monkeys or their tissues for vaccine production(25). In 1972 Stanford University vaccine researcher Leonard Hayflick pointed out that hundreds of thousands of people had been inoculated with SV40 virus found in polio vaccine made from monkey kidney cells. It is thought the SV40 virus can cause cancer(26). The preparation of vaccines using cells from dogs, chicks and ducks is also thought to be hazardous as cancer-causing viruses have been found in each case(25).
The cancer-causing viruses such as SV40 which contaminate tissues from primates, only become dangerous when
they, cross the species barrier(25) so the use of human cells to make human viral vaccines must be the safest approach.Today vaccines for many viral diseases including polio, rubella, measles smallpox, rabies and diseases caused by arboviruses such as yellow fever; can all be produced more safely from test tube cultures of human cells(25). In Britain, Sabin's polio vaccine is made from human cells(27) yet despite the dangers, most of the polio vaccine used throughout the world is still derived from African green monkeys and in some countries from rhesus monkeys(28). And although Salk's polio vaccine is traditionally made from monkey kidney tissue, research by the National Bacteriological Laboratory in Stockholm shows that this too can be produced from human cells(29).
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