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HIV Vaccine: Why There Is None Yet and How to Prevent HIV

Last updated November 1, 2026

HIV is a virus that attacks the body’s immune system. Without treatment, it can lead to AIDS, the most advanced stage of the infection. HIV has no cure, but today it can be prevented and treated.

Scientists have worked on an HIV vaccine for decades. There is still no approved vaccine that prevents HIV. This page explains why the work is so hard, what people can use to prevent HIV now, and where vaccine research stands.

HIV Today

HIV remains a major global health problem. The World Health Organization (WHO) estimates that HIV has claimed 44.2 million lives to date, and that it still spreads in every country.

According to WHO figures for 2025:

  • About 41.0 million people were living with HIV at the end of the year. Of these, 64% lived in the WHO African Region.
  • About 1.2 million people acquired HIV during the year.
  • About 570 000 people died from HIV-related causes.

Treatment has changed the outlook. With access to prevention, testing, treatment and care, HIV has become a manageable long-term health condition. In 2025, 88% of people living with HIV knew their status. Of those, 89% were receiving antiretroviral therapy (ART), and 95% of people on ART had suppressed viral loads.

How HIV Spreads

HIV spreads through certain body fluids of a person who has the virus: blood, breast milk, semen and vaginal fluids. It can also pass from a mother to her baby during pregnancy and delivery.

HIV does not spread through ordinary daily contact, such as kissing, hugging, shaking hands, or sharing personal objects, food or water.

People living with HIV who take ART and have an undetectable viral load will not pass HIV to their sexual partners. This is one reason why early testing and treatment matter for everyone.

Why There Is No HIV Vaccine Yet

No preventive HIV vaccine has been approved by the U.S. Food and Drug Administration (FDA). Experimental HIV vaccines are only available in clinical trials. The U.S. National Institute of Allergy and Infectious Diseases (NIAID) says an HIV vaccine has proven to be among the most daunting scientific challenges.

Several problems make the work hard:

  • The virus changes a lot. HIV’s genetic diversity makes it difficult to target with a vaccine. A vaccine must protect against many different forms of the virus.
  • Large trials have disappointed. NIAID notes that the field has had disappointing results from large efficacy studies, and has had to learn and adapt after each one.
  • The right immune response is not yet defined. Researchers still need to define the “correlates of protection” for an HIV vaccine. These are the specific immune markers that show a person is protected.

What Earlier Trials Showed

Some trials have shown partial protection. In 2009, the RV144 trial showed for the first time that an investigational vaccine regimen could give a modest degree of protection against HIV. According to NIH, RV144 reduced HIV infection by about 31 percent.

Later, the Antibody-Mediated Prevention (AMP) studies tested antibodies given directly to people, not a vaccine. They found that broadly neutralizing antibodies could reduce HIV infection by up to 75 percent, but only for some strains of the virus.

Is It Safe to Take Part in a Trial?

A person cannot get HIV from a preventive HIV vaccine. These vaccines do not contain HIV. According to NIH, of the approximately 30,000 people who have taken part in HIV vaccine studies around the world in the last 25 years, no one has gotten HIV from any of the vaccines tested.

Where Vaccine Research Stands

Researchers are working from two directions. One is an “empirical” approach, which moves vaccine candidates into human trials quickly and learns from the results. The other is a “theoretical” approach, which designs vaccines based on how the immune system responds to HIV.

Current areas of work include:

  • Broadly neutralizing antibodies (bNAbs). These antibodies bind to parts of HIV that stay fairly similar across many variants. Scientists hope a vaccine can teach the body to make them.
  • Germline targeting. This technique tries to guide new (naive) B cells, step by step, to develop into mature B cells that can produce bNAbs.
  • T-cell responses. NIAID research found that a safe and effective HIV vaccine will likely need to stimulate strong responses from CD8+ T cells.
  • mRNA technology. mRNA-based HIV vaccine candidates are being tested in people in early-stage trials.

NIAID’s stated long-term aim is a vaccine strategy that triggers both bNAbs and T-cell responses with a single regimen. Even a partly effective vaccine could matter. HIV.gov notes that a vaccine that protects only some people, or gives less than total protection, could still have a major impact on transmission.

People who want to learn about HIV vaccine trials can search the ClinicalTrials.gov database. The NIH Vaccine Research Center also takes questions about taking part in vaccine studies.

How to Prevent HIV Now

While the search for a vaccine goes on, there are proven ways to lower the risk of HIV. WHO lists these steps:

  • Use a male or female condom during sex.
  • Get tested for HIV and other sexually transmitted infections.
  • For men, be circumcised.
  • Use harm reduction services if you inject drugs.

PrEP and PEP

Pre-exposure prophylaxis (PrEP) is HIV medicine that people without HIV take to lower their risk of getting it. Post-exposure prophylaxis (PEP) is HIV medicine taken after a possible exposure.

WHO recommends these PrEP methods:

  • Oral tenofovir (TDF)-based PrEP.
  • The dapivirine vaginal ring.
  • Long-acting injectable cabotegravir.
  • Long-acting injectable lenacapavir.

Lenacapavir has been approved by the FDA for HIV prevention. Long-acting injections may change how some people take prevention medicines.

Talk with a healthcare provider if you think PrEP or PEP may be right for you. If you think you were exposed to HIV, seek care quickly.

Testing and Treatment

HIV testing is simple. Rapid tests can give results on the same day, and people can also use HIV self-tests. No single test gives a full positive diagnosis. A trained health worker must do confirmatory testing.

Most people develop antibodies to HIV within 28 days of infection. People who had a recent high-risk exposure and test negative can have a further test after 28 days.

ART does not cure HIV, but it stops the virus from copying itself in the body. This lets the immune system get stronger and helps people live long, healthy lives. Pregnant women with HIV should start ART as soon as possible to protect their own health and their baby.

Why a Vaccine Still Matters

HIV medicines work well, but they can be hard to use over a lifetime. NIH notes that they can be difficult to get in some areas, may have side effects and high costs. Long-term treatment also needs strict use on a set schedule, which is difficult for many people. Researchers believe a preventive vaccine would be the most effective way to control or end new HIV infections.

Vaccines have already changed the course of many other diseases. Learn more about diseases and vaccines, how routine immunization protects children, and the malaria vaccines now given to young children in Africa.

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