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Vaccines

Before we talk about an HIV vaccine, it helps to understand how vaccines work:

What do vaccines do?

Vaccines stimulate your body's immune system to "recognize" harmful viruses or bacteria BEFORE you get infected. This allows your body to set up defenses against them, so that you won't get sick if you're exposed to them later.

Is there a vaccine for HIV?

No. There is currently no vaccine that will prevent HIV infection or treat those who have it.

Why don't we have an HIV vaccine yet?

Researchers have been trying to find an HIV vaccine since the virus was first identified in 1984—but, so far, they haven't been successful. That's because HIV does not act like other viruses for which we have vaccines, like measles or chickenpox.

In part, HIV is different from other viruses because the immune system never fully gets rid of it. Most people who are infected with a virus recover from the infection, and their immune systems "clear" the virus from their bodies. This is true even for viruses that can be deadly, like influenza.

Once your body has cleared a particular virus, you often develop immunity to it. This link between infection and immunity has helped scientists create vaccines that protect people without them having to get sick first.

But the human body can't seem to clear HIV. The antibodies it makes to fight HIV are not effective, and HIV is able to "hide" in the immune system and other cells in the body—where, without treatment, HIV does serious damage to the body's ability to fight disease.

To date, no person with an established HIV infection has managed to clear the virus. That makes it hard to develop a vaccine, because scientists don't yet know how to encourage the body to fight HIV once it's infected.

HIV also mutates, meaning the virus changes rapidly. This creates a challenge because vaccines are designed to protect you from one, or a very limited number, of viruses or bacteria. Because HIV now has many different strains, it is harder to develop a vaccine that will be effective.

For more information about the challenges related to discovering an HIV vaccine, see Dr. Anthony Fauci's Why there is no AIDS vaccine. (Fauci is director of NIH's National Institute for Allergy and Infectious Disease .)

If we develop a successful HIV vaccine, what would it do?

An HIV vaccine would help your immune system to protect itself against HIV. A preventative vaccine would keep you from getting infected with HIV in the first place. Preventative vaccines would work primarily by using some part of the genetic material or genes of HIV. Researchers hope that, by introducing these genes into your body (possibly through an injection, like other vaccines), they would stimulate your immune system to remember and attack the real virus should you ever be exposed to it. Since the genes in any vaccine would only be components of HIV and not the actual virus itself, you could not develop HIV infection from the vaccine.

Another type of vaccine, called a therapeutic vaccine, would either improve your immune system after you had already been infected, or eliminate the HIV infection entirely. Researchers hope that these vaccines will eventually help to strengthen your body's response to HIV after infection has already taken place. A therapeutic vaccine could reduce or eliminate the need for people living with HIV/AIDS to rely on antiretroviral medications.

Current HIV Vaccine Research

The CDC's HIV Vaccine Unit conducts and evaluates HIV vaccine trials in the United States and elsewhere. For more information, see CDC's Vaccine Development.

NIH currently conducts HIV vaccine research in multiple laboratories across the Institutes and the nation. For more information, see the National Institutes for Allergy and Infectious Disease's Vaccine Research Center.