Statement of the Hypothesis

Statement of the Hypothesis that an Experimental Polio Vaccine was Origin of HIV

Contemporary Women’s Issues, September 12, 2000

Theory suggests that an experimental polio vaccine introduced in Central Africa in the 1950s may have exposed the general population to the HIV virus

© 2000 World Health Organization


Since the beginning of the AIDS epidemic, there has been much speculation in both the scientific literature and in the popular press on the origin of HIV, the virus that causes AIDS. One theory, that HIV was spread to the general population by an experimental polio vaccine used in Central Africa in the 1950 ‘s, has been detailed by Mr. Edward Hooper in his book, The River(1999). This theory is not new. It has been described by other authors and was previously rejected by an independent panel of experts.

In his book, Mr Hooper outlines studies that needed to be completed in order to rule out the possibility that HIV was spread to the general population by an experimental polio vaccine. This included the testing of the retained samples of the experimental vaccine for the HIV, SIV (Simian Immunodeficiency Virus) and chimpanzee DNA. (The hypothesis states the vaccine was produced using chimpanzee kidneys.)

New Scientific Findings

This week (week of September 11th), the Royal Society in London met to examine the origin of HIV. Mr Hooper’s theory is one of several hypotheses being considered.

The following scientific findings presented to the Royal Society further reject Mr Hooper’s hypothesis.

* Genetic sequencing data suggests that HIV first entered the human population around 1930, well before the vaccine trials of the 1950’s.

* Using ultra sensitive molecular methods, the experimental polio vaccine samples (which have been in safe storage since the late 1950s), have recently been tested, and are negative for HIV, SIV and chimpanzee DNA. The latter finding rules out the hypothesis that chimpanzee kidneys were used in the preparation of these experimental vaccine samples.

* Moreover, the process used to manufacture the vaccine would not permit the experimental vaccine to be contaminated with HIV or SIV. Production of the experimental vaccine included treatment with trypsin (a powerful enzyme), freezing, thawing and filtration, each of which is known to destroy or remove HIV and SIV. This process would not support the transfer of HIV to the final vaccine product.


* These new findings are consistent with other epidemiological, biological and virological evidence and indicate that Mr Hooper’s hypothesis cannot be substantiated.

* The Sabin strain of the oral polio vaccine used in polio immunization is in NO WAY related to the experimental vaccine questioned by Mr Hooper (the “CHAT” vaccine). Modern vaccines are always tested before use and DO NOT contain HIV or SIV.

* Oral Polio Vaccine (OPV) is safe and effective and the recommended vaccine for the global effort to eradicate polio and certify the world polio-free by 2005. It is the only vaccine proven to stop transmission of the virus in developing countries. Using this vaccine, the global campaign to eradicate polio has achieved a more than 95 per cent decrease in the number of polio cases world-wide in the twelve years since it was launched, and is on track to eradicate the disease.

For more information, please contact Ms Christine McNab, Communications Officer, Global Polio Eradication Programme, WHO, Tel (+41 22) 791 4688 email mcnabc§, or Gregory Hartl, WHO Spokesperson, Geneva, Telephone (+41 22) 791 4458 Fax (+41 22) 791 4858, E-mail hartlg§ All WHO Press Releases and Fact Sheets can be found on Internet on the WHO home page: