A new paper claims that HIV infection may be impeded in individuals who had the smallpox vaccine:
[Dr. Raymond] Weinstein and his colleagues analyzed the behavior of white blood cells sampled from patients recently immunized with the smallpox vaccine. They found that after exposure to HIV, cells from immunized individuals were five times less likely to allow for HIV replication than the same cells taken from non-immunized patients.
This is presumably a relatively small effect on HIV transmission, although the story hypes it as a reason for differential infection rates in Africa. What I wonder is whether the observation enhances the hypothesis that CCR5 delta-32, the HIV resistance allele, once functioned as a smallpox defense.