What Are Vaccines and What Do They Do?
A vaccine—also called a “shot” or “immunization”—is a substance that teaches your body's immune system to recognize and defend against harmful viruses or bacteria.
Vaccines given before you get infected are called “preventive vaccines” or “prophylactic vaccines,” and you get them while you are healthy. This allows your body to set up defenses against those dangers ahead of time. That way, you won't get sick if you're exposed to them later. Preventive vaccines are widely used to prevent diseases like polio, chicken pox, measles, mumps, rubella, influenza (flu), hepatitis A and B, and human papillomavirus (HPV).
In addition to preventive vaccines, there are also therapeutic vaccines. These are vaccines that are designed to treat people after they already have a disease by strengthening the body’s natural immune response against the disease.
Is There a Vaccine For HIV?
No. There is currently no vaccine that will prevent HIV infection or treat those who have it.
Why Do We Need an HIV Vaccine?
Today, more people living with HIV than ever before have access to life-saving treatment with HIV medicines (called antiretroviral therapy or ART), which is good for their health and reduces the likelihood that they will transmit the virus to others if they adhere to their HIV medication. In addition, others who are at high risk for HIV infection have access to pre-exposure Prophylaxis (PrEP), or ART being used to prevent HIV. Yet, unfortunately, approximately 50,000 Americans and 2 million people worldwide became newly infected with HIV in 2014. To control and ultimately end HIV globally, we need a powerful array of HIV prevention tools that are widely accessible to all who would benefit from them.
Vaccines historically have been the most effective means to prevent and even eradicate infectious diseases. They safely and cost-effectively prevent illness, disability, and death. Like smallpox and polio vaccines, a preventive HIV vaccine could help save millions of lives.
Developing safe, effective, and affordable vaccines that can prevent HIV infection in uninfected people is the best hope for controlling and ultimately ending the HIV/AIDS pandemic.
The long-term goal is to develop a safe and effective vaccine that protects people worldwide from getting infected with HIV. However, even if a vaccine only protects some people who get vaccinated, or even if it provides less than total protection, it could still have a major impact on the rates of transmission and help control the pandemic, particularly for populations at high risk of HIV infection. A partially effective vaccine could decrease the number of people who get infected with HIV, further reducing the number of people who can pass the virus on to others.
A therapeutic vaccine could also benefit people living with HIV by helping slow the progression of the disease and preventing or delaying the onset of AIDS.
For more information, see the video below with Dr. Anthony Fauci, Director of NIH’s National Institute of Allergy and Infectious Diseases (NIAID).
Why Don't We Have An HIV Vaccine Yet?
HIV is a very complex, highly changeable virus, which makes speedy development of a successful preventive HIV vaccine very difficult, but not impossible. It also takes many years to conduct the research, including the careful clinical testing that will lead to a safe and effective vaccine.
Researchers from around the world have been working for more than two decades to create a vaccine that will protect people against HIV infection. NIAID supports the HIV Vaccine Trials Network (HVTN), an international collaboration of scientists and other professionals searching for an effective and safe HIV vaccine. The U.S. Military HIV Research Program (MHRP) is also engaged in HIV vaccine research and led a large collaboration of clinical scientists also funded by NIAID in implementing a vaccine trial that was the first to show modest protection against HIV infection. (For more on this trial, see “What’s the Latest on HIV Vaccine Research,” below.)
How Is HIV Different From Other Viruses?
In part, HIV is different from other viruses because your 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—meaning it won’t make you sick the next time you are exposed to it. Different civilizations and cultures throughout history have known that protective immunity can also be developed by exposing people to dead or weakened viruses that will protect them from deadly diseases later.
But the human body on its own can't seem to fully clear HIV and develop immunity to it. The antibodies your immune system makes to fight HIV typically are not protective, or develop too late after infection to overcome the virus. Plus, HIV actually targets, invades, and then destroys some of the most important cells in your immune system itself. This means that, over time, HIV does serious damage to your body's ability to fight any disease.
For more information about the importance of a preventive HIV vaccine, see Dr. Anthony Fauci's Ending AIDS — Is an HIV Vaccine Necessary?
What’s The Latest On HIV Vaccine Research?
Scientists are continuing to create and test HIV vaccines—in the lab, in animals, and even in human subjects. These vaccine trials help researchers to learn whether a vaccine will work and if it can be safely given to people.
In 2009, MHRP and collaborating researchers published findings from a large-scale HIV vaccine trial in Thailand called RV144. That trial involved more than 16,000 adults and showed that a combination vaccine was safe and could prevent about 31 percent of new infections. The scientific community, with leadership from NIAID, is working collaboratively to build on what was learned from RV144 to help speed the process of developing an HIV vaccine. Those efforts have provided information that certain antibodies may serve either as a signal for, or play a direct role in, decreasing the risk of becoming HIV infected. This has led to a better understanding of the type of immune response that may be needed for a preventive HIV vaccine to be effective. In 2015, NIAID and collaborators launched HVTN 100, a NIAID-sponsored clinical trial in South Africa that is testing an experimental HIV vaccine regimen based upon findings from the RV144 trial. For more information on the RV144 trial, see the U.S. Military HIV Research Program.
NIAID is also studying other vaccine approaches, including developing vaccines that might work by stimulating uninfected people’s immune systems to produce broadly neutralizing antibodies capable of blocking the infectivity of a wide range of HIV strains. Several other NIAID-sponsored clinical trials are ongoing. Read NIAID’s bulletin on the state of vaccine research for HIV Vaccine Awareness Day.
For more information about HIV vaccines and how you can get involved in HIV vaccine trials, check out Be The Generation. For information about specific HIV vaccine trials, go to the HVTN website at www.HVTN.org or http://www.AIDSinfo.nih.gov, which has information about all HIV trials.
Related Topics on AIDS.gov
Last revised: 04/15/2016