At this time no vaccine is available to prevent people from becoming infected with HIV and studies of various vaccines have been disappointing. The virus mutates (that is, its surface proteins change) quickly. Because vaccines are usually directed against surface proteins in an effort to kill the virus, such subtle but important changes in the virus over time mean that a vaccine that may be effective at one time may not be effective a short while later. With the rapid spread of HIV throughout the world—especially in areas where people are not able to afford expensive treatments once they become infected—the development of an effective vaccine is imperative.
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