The Doctor's World column "New Book Challenges Theories of AIDS Origin" on Nov. 30 describes the hypothesis that H.I.V., the virus that causes AIDS, was initially transmitted to humans during the first large-scale trials of oral polio vaccine in what was then the Belgian Congo. Although we are not named in the article, it is common knowledge in the scientific community that we conducted those trials. The hypothesis is based on the suggestion in a recently published book that we used chimpanzee cells to prepare the vaccine, and that these cells were, unknown to us, contaminated with a precursor of the human AIDS virus.
We wish to state categorically that no chimpanzee tissues were used by us for polio vaccine production.
Most scientists believe that H.I.V. originated from a chimpanzee virus, but there are other explanations for the transmission to humans that have nothing whatsoever to do with polio vaccination. The early cases of AIDS appeared where they would be expected to occur, in sites of relatively high population density.
Moreover, two independent analyses of the probable timing of the crossover of H.I.V. from chimpanzees into humans give dates far earlier than 1957-59, the years in which our polio vaccine was used in the Congo. We believe the book is likely to increase the concerns in Africa about the safety of polio vaccines, and indeed of other badly needed vaccines.
DR . STANLEY A. PLOTKIN Doylestown, Pa. DR . HILARY KOPROWSKI Philadelphia
Dr. Plotkin is an emeritus professor of pediatrics at the University of Pennsylvania; Dr. Koprowski is a professor of microbiology and immunology at Thomas Jefferson University.
The Doctor's World column on AIDS origins makes valid points in the argument that Edward Hooper's theory of vaccine contamination should be explored further. Those scientists who feel the legitimization of Hooper's theory would tarnish public confidence in the safety of vaccines are not only shortsighted, but naïve.
Anyone who has followed the AIDS epidemic has pondered either in public or private numerous rumors and theories, from tainted vaccines to government conspiracies. With no cure in sight, more research into the origins of this epidemic not only has the potential to win tangible scientific results but also the trust of millions who often feel they are only receiving information that has been deemed palatable to the public.
CODY LYON New York
Polio vaccines and the origin of AIDS
in the section on The River.
It is located on Brian Martin's website on suppression of dissent.