D. C. Sessions wrote:
Apparently, smallpox may have been good for
something after all: it may have given some
partial immunity to AIDS

http://news.bbc.co.uk/2/hi/health/8686750.stm

Well, OK, the vaccine seems to be of some use
against HIV/AIDS. But it's not too large a
stretch to conclude that smallpox might have
had the same effect.

The study also showed some long-term changes in the levels of some
cytokines. I was a bit surprised by this, because people are normally
exposed to so many different antigens, that I wouldn't expect this to
happen. This also raises issues about the long-term effects of the
vaccines, particularly with regard to autoimmune diseases and other
infections.

Of course, this is a lot to base on one study of just 20 subjects.

jeff