OPV AIDS hypothesis
According to the oral polio vaccine (OPVA) AIDS hypothesis, the AIDS pandemic originated from live polio vaccines prepared in chimpanzee tissue cultures (at least some of which were almost certainly contaminated with chimpanzee SIV) which were administered to up to one million Africans between 1957 and 1960. The specific populations, who may not have been properly informed of the risks before volunteering for the vaccination, were the first in the world to experience HIV-1 infections and AIDS some five years later.
In particular the experimental oral vaccine, called CHAT-1, is claimed to have been contaminated with simian immunodeficiency virus (SIV), a group of viruses endemic to African primates and widely accepted as the origin of HIV. Recent evidence shows that CHAT-1 may have been concentrated in African facilities using tissue cultures made from chimpanzee kidneys (more importantly, utilizing chimpanzee serum, containing macrophages, the target of immunodeficiency viruses).
Proponents of the OPV AIDS hypothesis include journalist Edward Hooper as well as scientists Louis Paschal and the late W.D. Hamilton.
The OPV AIDS hypothesis is contradicted by a large mass of scientific evidence, and is considered to be incorrect by the scientific community.

# Polio vaccines
Two vaccines are used throughout the world to combat polio.  The first polio vaccine, developed by Jonas Salk, is an inactivated poliovirus vaccine (IPV), consisting of a mixture of three wild, virulent strains of poliovirus, grown in a type of monkey kidney tissue culture (Vero cell line), and made noninfectious by Formalin treatment. The second vaccine, an oral polio vaccine (OPV), is a live-attenuated vaccine, produced by the passage of the virus through non-human cells at a sub-physiological temperature. The passage of virus produces mutations within the viral genome, and hinders the virus's ability to infect nervous tissue.
Both vaccines have been used for decades to induce immunity to polio, and to stop the spread of the infection. However, OPV has several advantages; because the vaccine is introduced in the gastrointestinal tract, the primary site of poliovirus infection and replication, it closely mimics a natural infection. OPV also provides long lasting immunity, and stimulates the production of polio neutralizing antibodies in the pharynx and gut. Hence, OPV not only prevents paralytic poliomyelitis, but also, when given in sufficient doses, can abort a threatening epidemic. Other benefits of OPV include ease of administration, low cost and suitability for mass vaccination campaigns.

## CHAT vaccine
Oral polio vaccines were developed by several groups, one of which was lead by Albert Sabin. Another group, led by Hilary Koprowski, developed its own attenuated vaccine strains. In 1952 Koprowski developed the TN strain at the Wistar Institute in Philadelphia, later identified as type 2 poliovirus. A type 1 strain, called SM, was reported in 1954. A less virulent version of the SM strain, called CHAT, was reported by Koprowski in 1957. In 1958, the National Institutes of Health created a special committee on live polio vaccines. The various vaccines were carefully evaluated for their ability to induce immunity to polio while retaining a low incidence of neuropathogenicity in monkeys. Based on these results, the Koprowski strains were eliminated and the Sabin strains were chosen for worldwide distribution.
Between 1957 and 1960, however, Koprowski would continue to administer his vaccine around the world. In Africa, the vaccines were administered to roughly one million people in the Belgian territories; now the Democratic Republic of the Congo, Rwanda and Burundi. During the same period, Koprowski immunized 40,000 children in Germany and more than seven million in Poland with his attenuated strains.
In Africa, it was standard to transport a small amount of the original vaccine and then locally amplify it using local facilities and tissue cultures harvested from native animals. In South Africa, African green monkey tissue was used to amplify the Sabin vaccine. In French West Africa and Equatorial Africa, baboons were used to amplify a vaccine from the Pasteur Institute. In Poland, the CHAT vaccine was amplified using Asian macaques.

# Recent claims
In 2003, Edward Hooper and colleagues travelled to the Democratic Republic of Congo and claimed to uncover testimony supporting the OPV hypothesis. In the Congo, the Laboratoire Medical de Stanleyville (LMS) was responsible for testing the CHAT vaccine and performing the initial set of vaccinations. A few miles from LMS was Lindi Camp, a chimpanzee colony at which more than 500 chimps and bonobos, collected from a 300km radius, were sacrificed between 1956 and 1960.
In Kisangani, Hooper talked to former lab technicians that had worked on the vaccination program at LMS. Jacques Kanyama, a virology technician, alleged that batches of CHAT had been prepared locally, a possibility formerly denied by Belgian and American staff who claimed that the lab was too primitive and lacked equipment. According to Kanyama, Paul Osterrieth, in charge of the virology department, had been producing an oral polio vaccine on-site. Philip Elebe, a microbiology technician, claimed that tissue cultures were being produced from Lindi chimpanzees. Osterrieth disputes these claims, saying that no vaccine was prepared locally and that only the CHAT vaccine from America was used.

# History
San Antonio physician Eva Lee Snead was the first person to voice the theory that AIDS could have crossed to humans via an infected polio vaccine. However she  also argued, incorrectly that SV-40 might be a precursor to HIV.
In May 1987 Louis Pascal heard a radio broadcast by Dr. Snead explaining her theory. By reading medical journals from the 1950s and 1960s and comparing with what was known about the first cases of HIV infection, he concluded that Koprowski's CHAT Type 1 vaccine administered in Belgian Congo between 1957 and 1960 was a likely source. Pascal wrote a paper on the theory, which was mailed to prominent researchers , but received no response apart from a note of thanks on behalf of Luc Montagnier. He next submitted the paper to three scientific, and two multidisciplinary journals, none of whom would publish it. The Lancet and New Scientist gave no reasons for rejection, but Nature said that "while the theory cannot be ruled out, it does not seem readily to fit the epidemiology of AIDS".
In the same year Blaine Elswood, an AIDS treatment activist who had developed similar ideas, contacted the journalist Tom Curtis about a "bombshell story." Curtis investigated the story and published an article in  Rolling Stone 1992.. 
Hilary Koprowski sued the Rolling Stone and Tom Curtis for defamation. The magazine published a "retraction" which  praised Dr. Koprowski and absolved him from any blame for the introduction of AIDS to the human population: "we never wished to suggest that it has been scientifically proven that Koprowski is the father of AIDS." However the "retraction" also reiterated that the OPV theory was "one of several disputed and unproven theories". Rolling Stone  had to pay $US 1 million in damages and around $US 500,000 for legal fees. The legal action cost Dr Koprowski around $US 300,000.
A few scientists, notably the biologist W.D. Hamilton thought the theory required serious investigation, but they received little support from the scientific community. Hamilton wrote a letter to Science in 1994 supporting Pascal and Curtis, but it was rejected by the editors.
Journalist Edward Hooper, who had already begun to investigate the origin of AIDS when the OPV theory was first put forward gradually became convinced of its truth. After nine years of investigations, he detailed the theory and evidence in his 1999 book, The River. In 2004, the Origin of Aids, a TV documentary strongly supportive of the OPV theory, appeared on television stations globally.

# Scientific refutation
For 15 years, the OPV AIDS theory has been criticized by members of the scientific and medical establishment as being unfounded, unlikely or inconsistent with HIV epidemiology. In October 1992, the journal Science ran a story titled "Panel Nixes Congo Vaccine as AIDS source," describing the findings of an independent panel which found each proposed step in the OPV-AIDS hypothesis "problematic". The panel also noted that at least one case of HIV/AIDS was described prior to the OPV trial, and concluded that:
...it can be stated with almost complete certainty that the large polio vaccine trial... was not the origin of AIDS.
In 2001, three articles published in Nature examined various aspects of the OPV-AIDS hypothesis, as did an article published in Science. In every case, the studies' findings argued strongly against any link between the polio vaccine and AIDS. An accompanying editorial in Nature concluded:
The new data may not convince the hardened conspiracy theorist who thinks that contamination of OPV by chimpanzee virus was subsequently and deliberately covered up. But those of us who were formerly willing to give some credence to the OPV hypothesis will now consider that the matter has been laid to rest.
Ongoing claims by proponents of the OPV-AIDS hypothesis that Kisangani chimpanzees were, indirectly, the true source of HIV-1 were again addressed in a 2004 study published in Nature. Here, the authors found that while SIV was present in chimpazees in the area, the strain of SIV infecting these chimpanzees was phylogenetically distinct from all strains of HIV, providing direct evidence that these chimps were not the source of HIV in humans.