The Wistar Institute, which developed an attenuated live polio vaccine in the 1950s, said it would allow two independent laboratories to test lab specimens to prove that its research in Africa was not responsible for initiating the transfer of SIV from chimpanzees to humans, where it is thought to have mutated into HIV. The decision came after the release of a new book by British journalist Edward Hooper, titled "The River: A Journey to the Source of HIV and AIDS," which argues the vaccine was produced with tissue from chimpanzees infected with SIV and then tested on children. Researchers directly involved with the development and testing of the polio vaccine in the 1950s adamantly denied the accusations and said the chimpanzees were used to test the vaccines, not produce them. Four years ago, Swedish scientists tested one of the samples to dispel similar arguments, but the new testing will involve both lots in order to reach a final conclusion.