As with all viral infections HIV too has a very small armamentarium of drugs against it. Since viruses multiply within living human cells, drugs to act on them, have to damage the human cell as well.

Viruses being extremely small and having a very simple structure, drugs have a few sites to act on (unlike as in bacteria, where they can act on the cell wall, the nucleus, the cytoplasm, the organells etc.) to disable them.

As for the vaccines, they help us fight diseases by acting on the immune system. Unfortunately in AIDS it is this immune system itself, which is under attack. Secondly, the virus (like the common cold virus) is known to alter its structure when inside the body thereby rendering the vaccine useless. This is so because the vaccine is very specific and only on a fixed and similar structure. Even a minute change renders the vaccine ineffective. Naturally it is difficult to synthesise vaccines against all the structural variations.
 

ANTIRETROVIRAL THERAPY (DRUGS USEFUL IN AIDS)

1)     Azidothymidine
2)     Zidovudine
3)     Didanosine
4)     Zulcitabine
5)     Lamivudine
6)     Nevirapine
7)     Saquinavir
8)     Ritonavir
9)     Indinavir

Note:
Drugs 1 to 5 form one group
6 the 2nd group
7 to 9 the 3rd group

Different group drugs act at different sites and by different mechanisms thereby killing the virus.

What is now being promoted is a cocktail of drugs from 2 or more different groups.