Did the Eradication of Smallpox Accidentally Help the Spread of HIV?

By Andrew Moseman | May 18, 2010 10:54 am

Smallpox_vaccineWith smallpox largely eradicated around the world, health organizations phased out the smallpox vaccine between the 1950s and 1970s (the last natural case of the disease was seen in 1977, in Somalia). During that span, Raymond Weinstein says, the AIDS crisis broke out in force. And in a study in BMC Immunology, he argues those two events could be connected.

Supposing that smallpox vaccination could have some effect on a person’s susceptibility to HIV, researchers led by Weinstein tested the idea on cells in a lab. They took immune cells from 10 people recently vaccinated against smallpox and 10 people never vaccinated. HIV, they found, was five times less successful at replicating with the cells of vaccinated people.


The researchers believe vaccination may offer some protection against HIV by producing long-term alterations in the immune system, possibly including the expression of a receptor called CCR5 on the surface of white blood cells, which is exploited by the smallpox virus and HIV [BBC News].

Any finding that expands knowledge of how HIV replicates could be an important one. And while this small study can’t prove Weinstein’s assertion is correct, the argument is, at the very least, plausible. Says Weinstein:

“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. However, all of these have been either disproved or do not sufficiently explain the behaviour of the HIV pandemic” [Press Association].

Related Content:
DISCOVER: Whatever Happened to… Smallpox?
DISCOVER: 20 Things You Didn’t Know About… Lab Accidents
DISCOVER: Killer Pox in the Congo
80beats: Researchers Track the HIV Virus to a Hideout in the Bone Marrow
80beats: S. African HIV Plan: Universal Testing & Treatment Could End the Epidemic

Image: CDC

CATEGORIZED UNDER: Health & Medicine
  • derek

    Couldn’t unprotected sex and a population that has no concept of what HIV is or how it spreads be to blame for the rapid spread?

  • rabidmob

    Your assumption would then be that they were not that way prior to the discontinuation of the small pox vaccine.

    In other words it is not relevant to the study.

    You are however correct as to what is large contributor to the fact of, but not a reason for a sudden spike.

  • Quinn O’Neill

    According to WHO:
    “Epidemiological studies have demonstrated that vaccination protects against smallpox for less than five years after primary vaccination and that substantial but waning immunity can persist for ten years or longer.”

    Vaccination is typically performed in early childhood. If unprotected sex is a big part of the problem, and those engaging in this practice can be assumed to be over the age of 15, then recently vaccinated people weren’t the best choice for the study.

  • pheldespat

    Correlation does not imply causation.

  • Jennifer Angela

    I´ve read once that the HI-virus was originally spread due to a human being either 1. fighting against a monkey (which had HIV), or 2. drinking the blood of an AIDS-infected monkey (drinking monkey blood is a tradition among some african tribes….young grooms drink blood in order to be capable of satisfying their young brides during their wedding night more than they normally would be…), 3. some human being might have had sexual intercourse with a monkey, which had the HI-virus.

  • Jennifer Angela

    As I have discovered right now, there is also a fourth theory on how come people “received” the HI-virus from monkeys: you can read all about it on the following website:


  • Jennifer Angela

    Frankly I don´t think there is a direct link between vaccines and the HI-virus. But if anybody ever manages to cure those Aids-infected monkeys, there would be a cure for Aids.

    Personally, I have always been awfully cautious about protecting myself against Aids, which might be the reason why I don´t have the HI-virus, but I think we all need to consider, that sometimes people DO have back luck: I have read a true story about a female tourist, who was actually a virgin before having been infected with Aids due to a summer holiday love affair. That´s what I call bad luck!

  • Rebecca

    I don’t think the scientists are arguing that stopping small pox vaccination CAUSED HIV. As Jennifer’s link pointed out, scientists believe HIV (or SIV) was first transmitted to humans in the 1930s. Moreover, monkeys and chimps don’t have HIV, they have SIV. Diseases spread between species by being transmitted (often through eating the animal meat or close contact in farming or hunting) to another species and then mutating in such a way that they affect the new species.

    The question is what made HIV a pandemic in the 80s? It seems possible that stopping the small pox vaccinations allowed the virus to mutate faster in non-vaccinated individuals thus increasing the spread of the disease. Of course, this is all correlation at this point.

    Re: Quinn – As the article says, “The researchers believe vaccination may offer some protection against HIV by producing long-term alterations in the immune system” In other words, the antibodies that protect against small pox may become ineffective after 5 years but if the vaccination causes permanent/long lasting changes to the immune system (esp. because it’s given as a child when the immune system is developing), it is plausible that it could have contributed to the spread of HIV.

  • Quinn O’Neill


    If alteration to the CCR5 receptor confers immunity to both HIV and smallpox, then protection against HIV shouldn’t outlast protection against smallpox. Though, it’s possible that persistent changes to the receptor provide some protection against both viruses beyond 10 years. I may have wrongly assumed that the article was implying greater protection against HIV than would persist against smallpox 10 years after vaccination.

  • James



Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


80beats is DISCOVER's news aggregator, weaving together the choicest tidbits from the best articles covering the day's most compelling topics.

See More

Collapse bottom bar