No vaccination is possible for AIDS for following reasons:
HIV has a high capability to form different kinds of variants.
Some HIV-infected immune cells go into a dormant, or latent, state and does not make new virus. HIV can hide in this “ latent reservoir ” for a long time.
HIV uses the genetic material of T- helper cells by attaching its viral genetic material with the genetic material of the T-helper cell to produce more viral products. So, vaccination against the virus destroys our own T- helper cells consisting of the viral genetic material.