The AIDS pandemic was not sparked by oral polio vaccines used in Africa in the 1950s that were contaminated with a chimpanzee virus, new research confirms.
The controversial theory on the origins of AIDS had been dismissed by many medical experts who said there was no scientific evidence to support it.
But doubts about vaccine safety have persisted and have been blamed for hampering World Health Organizationefforts to stamp out polio.
This latest research, published in the current issue of the journal Nature, provides more evidence against a link between HIV and the oral polio vaccine (OPV).
A team of researchers led by Assistant Professor Michael Worobey of the University of Arizona discovered a new strain of chimpanzee virus near Kisangani in the Democratic Republic of Congo that was very different from HIV.
The researchers said this was more evidence that these chimpanzees could not have been the source of human AIDS.
“The locally circulating strain [of the chimpanzee virus] is very distantly related to HIV. It is not a virus that could have been the progenitor and therefore HIV did not come from that region,” Worobey said.
He added that chimpanzees near Kisangani were endemically infected with simian immunodeficiency virus that was very different from the human strain.
But author Edward Hooper, who wrote about the polio vaccine-AIDS theory in his book The River, said Worobey’s conclusion was wrong and did not refute the theory.
“Although Worobey’s new research is helpful, the chimp groups his team has sampled are far from being representative of the chimpanzees that were used for the polio vaccine research,” Hooper said.
Origin of a pandemic
About 40 million people worldwide are living with HIV/AIDS.
Scientists generally believe that a chimpanzee virus jumped species when a human was bitten by a monkey or by people eating contaminated monkey flesh.
But the oral polio vaccine OPV/AIDS theory suggests chimpanzees from the Democratic Republic of Congo were the source of the virus and that scientists inadvertently trigged the AIDS pandemic with vaccines contaminated with the monkey virus.
Worobey and his colleagues said their data, along with information showing that the spread of HIV to humans started in the 1930s, and the absence of detectable chimpanzee virus or DNA in stocks of the original vaccines “should finally lay the OPV/AIDS theory to rest”.
“Given the fears about the safety of polio vaccines are currently threatening the global campaign to eradicate the disease, our clear-cut evidence against one of the key sources of concern is timely,” Worobey added.
Three states in northern Nigeria have suspended a polio immunisation program because of fears it could contain HIV and cause infertility.
The WHO launched an initiative to eradicate polio in 1988 but people in Nigeria, India, Pakistan, Egypt, Afghanistan, Niger and Somalia still have the illness.