When Acquired Immune Deficiency Syndrome (AIDS) first burst onto the public consciousness in the 1980s, many public health officials were optimistic that a vaccine for the disease would be developed by the 1990s. As the 1990s wore on with no sign of an AIDS vaccine or cure, some members of the public lost faith in the public health establishment. With numerous vaccines on the market for other diseases, the lack of a vaccine for AIDS was questioned. The reasons behind the difficulty in developing an AIDS vaccine are extremely complex, and some scientists are concerned that a vaccine may never actually be developed.
A traditional vaccine is designed to prevent disease, but not necessarily infection. The polio vaccine, for example, introduces antibodies into the human body to help it fight polio when it is exposed to the disease. Someone who has been vaccinated for polio can still be infected with polio, but the infection will not enter the nervous system and lead to polio disease. An AIDS vaccine, however, must prevent infection, because the body cannot be taught to fight the virus naturally. Since AIDS works from within the immune system, the body is unable to recognize and fight it.
Developing a vaccine which prevents infection is extremely difficult. Most experiments with a vaccine for AIDS have shown that a vaccination may be able to help stave off the progression into full-blown AIDS, but that preventing infection may prove to be a challenge. Partly this is due to the way in which AIDS works. However, it is also due to the nature of the virus itself. AIDS, unlike many other viruses which humans vaccinate against, is extremely diverse and versatile.
AIDS originally evolved in monkeys, and like other diseases of non-human origin, it mutates extremely rapidly to adjust to the differences of the human body. These rapid mutations mean that the virus changes dramatically, and that AIDS five years after the development of a theoretical vaccine will be radically different, potentially making the vaccine useless. AIDS is also broken up into several groups, or clades. Each clade contains different genetic information, and while each one has a geographic center, an effective AIDS vaccine would need to prevent infection from all clades of AIDS, because of the global nature of human interactions.
Research to develop an AIDS vaccine continues, while scientists also work on drugs which may help to treat the condition. However, many public health advocates have shifted their focus to prevention education, rather than wait for an AIDS vaccine.