[AdmSmith]

There are two genetically distinct types of HIV, HIV-1 and HIV-2. The two types are about 15-30% different at the DNA level. Both strains cause AIDS, although HIV-1 appears to be more virulent than HIV-2. There is some evidence that infection with HIV-2 may help protect against subsequent infection with the more virulent HIV-1. Epidemiologically, HIV-1 has spread around the world, while HIV-2 is mostly restricted to western Africa.
http://www.bioquest.org:16080/bedrock/problem_spaces/hiv/background.php

I am not updated on recent progress on vaccines, but some years ago the problem was to find a vaccine that would produce significant numbers of memory T lymphocytes, which are important in killing an infection. I do not think that the efficacy of a future vaccine would be different for the subtypes of HIV-1.

[AdmSmith]

I would add that since HIV-2 may help protect against subsequent infection with the more virulent HIV-1, then ther is a hope for a vaccine.

[CobaltBlue]

HIV-2 has a very different progression than HIV-1 - a prolonged asymptomatic period, and it appears to different receptors. It's widely reported to be "less virulent" - which may indicate that Africans have been exposed to it in the past and "developed immunity" - that is, the non-immune ones died out already. I don't think it conveys immunity to HIV-1.