Scientists have more evidence to disprove a theory that an oral vaccine against polio caused AIDS. The controversy has halted polio vaccination drives in parts of Nigeria. According to the theory, researchers developed the polio vaccine in the 1950s using tissues from chimpanzees in what is now the Democratic Republic of Congo. Those tissues may have been contaminated with a virus that then mutated to become HIV, the virus that causes AIDS.
Scientists agree that HIV is closely related to a chimpanzee virus called SIV. However, Evolutionary biologist Michael Worobey studied the genetic makeup of HIV found in the region where the polio vaccine was developed. "What we found was not a sister to HIV-1, but a very distant cousin," he said.
Too distant, he added, to have evolved into the virus causing the global AIDS pandemic. He said that HIV is much more closely related to viruses found in chimpanzees from west of the Democratic Republic of Congo, far from where the polio vaccine was developed. Mr. Worobey hopes the study puts to rest the idea that the polio vaccine caused AIDS, and allows the vital vaccination program to resume. His study appears in the British journal "Nature."