Both in vitro research and breakthrough technology have allowed scientists to actually grow the polio virus and visualise it, as seen here.
Animal experimentation actually delayed this much-needed vaccine throughout the first half of the 20th century.
When polio first appeared around 1835, it rapidly paralysed and killed its victims. In 1908, a virus was suspected and scientists began working on a vaccine. Note: In developing vaccines, it's crucial to determine how the infection enters the body. Luckily, pathologists discovered the polio virus in human intestines as early as 1912, suggesting entrance through the digestive tract.
Meanwhile, researchers successfully infected monkeys with polio. But because monkeys contract polio nasally rather than orally, this "triumph" only postponed the development of an effective vaccine for decades. Incredibly, the scientists working on the vaccine chose to ignore the human digestive data in favour of the monkey data!
It is true that a "vaccine" was derived from animal experimentation. But manufactured from monkey tissue, this "cure" resulted in six human deaths and 12 cases of paralysis. It was abandoned. Further animal experimentation led to the development of a nasal treatment, which only caused permanent olfactory damage to the children tested. [10-11]
In 1941, Dr. Albert Sabin studied human autopsies to finally disprove the nasal theory. He found the virus confined to the gastrointestinal tract, as had been documented nearly 30 years earlier.
Sabin later denounced the monkey model blunder:
"... prevention was long delayed by the erroneous conception of the nature of the human disease based on misleading experimental models of the disease in monkeys."
Finally, in 1949, Nobel Prize winner John Enders paved the way for a vaccine by growing the virus in tissue cultures. Though the vaccine could have been produced from human tissue, convention prevailed and manufacturers opted to use monkey tissue instead. Containing the live virus, the animal-based vaccine infected 204 people with polio and resulted in 11 documented deaths. It also resulted in at least one virus (SV4O) jumping the species barrier and infecting humans.
Because of that, the polio vaccine is now grown in human diploid-cell culture rather than animal tissue.