Scientists argue that receiving the smallpox vaccine prevented the AIDS-causing virus from multiplying as well as it does now. Smallpox immunizations were gradually reduced between the 1950s and the 1970s. Today, only scientists and medical professionals who work with smallpox receive the vaccine.
"There have been several proposed explanations for the rapid spread of HIV in Africa, including wars, the reuse of unsterilised needles and the contamination of early batches of polio vaccine," Dr Raymond Weinstein, the study's lead researcher, told the British Broadcasting Corp. "However, all of these have been either disproved or do not sufficiently explain the behavior of the HIV pandemic."
The researchers say that HIV has been spreading exponentially since smallpox was eradicated and widespread vaccines were discontinued.
"60 Minutes" Coverage on AIDS in Africa