The London Times – May 11, 1987
Smallpox vaccinations followed a ‘ring’ strategy, vaccinating everyone in the areas around new cases. It was often these very same areas where HIV erupted a few years later. So many of those who developed AIDS had, in fact, received smallpox vaccine.
This is a powerful, live vaccine that provides at least partial lifelong immunity. It is not like flu vaccine, whose immunity wanes in several months. Back when the smallpox campaign was active, most Africans had not been receiving any routine smallpox vaccinations prior to the campaign. And dirty needles were an ongoing problem. [I myself received a smallpox booster in 1972 in Nigeria, from a glass needle sterilized by sitting in a bowl of alcohol. Luckily I can still tell the tale.–Nass]
Smallpox vaccine may improve the ability of immune cells to fight the HIV virus. Regardless, the epidemiological fact is that many cases followed vaccination within a short span of years.