Before work on a vaccine could progress through the various phases, large numbers of the bacteria or viruses of interest had to be grown in the lab. Various nutritional media could be used to grow most kinds of bacteria. However, viruses require live cells in order to live and reproduce. Therefore, before cell culture techniques were developed, viruses had to be injected into animal hosts. Monkeys were often used since they get many of the same diseases we do. In the early development of the polio vaccine, polioviruses grown in monkeys were then used to vaccinate humans. However, this turned out to be very dangerous because some of the people receiving the vaccine got paralysis in the limb where it was introduced.
Scientists then tried to grow human cells in the lab to avoid these dangers. In 1936, Albert Sabin and Peter Olitsky at the Rockefeller Institute successfully grew poliovirus in a culture of brain tissue from a human embryo. After that, cell culture lines were developed from other types of tissue such as skin and muscle. Today, cell cultures use particular mammalian cell lines.
