HIV vaccines: Where are we now?
Although the latest treatments for HIV significantly increase a person's lifespan, no vaccine is yet available to help prevent HIV.
Current HIV prevention techniques centre on safe sex messages.
Vaccine development can take many years. For example, it took 47 years to develop a polio vaccine.
In 2014, one leading British HIV researcher predicted there would be a defining moment in HIV vaccine research by the end of the decade, Professor Jonathan Weber, from Imperial College London, has been working towards HIV jabs since 1985.
HIV vaccine challenges
Developing an HIV vaccine has challenges, including:
- HIV makes copies of itself very quickly
- Many types of HIV exist, and new types continue to arise
- HIV has developed clever ways of “outwitting” the immune system. Consequently none of the people infected by HIV have ever completely cleared it from their bodies
- Scientists are still trying to understand the specific ways the immune system needs to respond to prevent HIV infection
Types of HIV vaccines being tested
Two main types of HIV vaccines are currently being tested - preventive and therapeutic vaccines.
Preventive HIV vaccines:
- Are tested in people who are HIV negative
- Train the immune system to “recognise” and fight off HIV before it can establish infection and make the person unwell
- Are currently being tested in more than 35 trials in about 25 countries
- May one day work with varying degrees of success - by preventing infection in all, most or some people, by blocking continued infection or by delaying or preventing the development of AIDS
Therapeutic HIV vaccines:
- Are tested in people who are already HIV positive but who have healthy immune systems
- Help control infection and delay the progression of the disease by stimulating the immune system to identify and kill HIV-infected cells, and by preventing or limiting HIV from making copies of itself
- Are currently being tested in just a few trials
Because they don't contain live HIV, these HIV vaccines cannot give a person HIV. However they might prompt the body to produce antibodies to HIV.
How preventive HIV vaccines are tested
Before being tested in humans, HIV vaccines are tested in laboratories and animals. A specific HIV vaccine can take almost a decade of testing in humans before it would be considered safe for use by the public. Vaccines typically go through three phases of clinical trials:
- Phase 1 involves small numbers of healthy, HIV-negative volunteers and lasts between 12 and 18 months. It tests for the safety and best doses of the HIV vaccine. If this phase goes well, the study can go on to the next phase.
- Phase 2 involves hundreds of healthy, HIV-negative volunteers and can last for up to two years. This phase refines doses and tests the immune response, as well as the safety of the HIV vaccine. If this phase goes well, researchers then conduct the next phase.
- Phase 3 involves thousands of healthy, HIV-negative volunteers and can last for three to four years. It is the best test of whether the HIV vaccine is effective and safe.
In all three phases of HIV vaccine testing, participants are urged to continue using safer sex practices. They are not, as some people believe, deliberately exposed to HIV after vaccination.