Types of HIV Vaccines Being Tested continued...
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 studies
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 that would show up on a blood test.
How Preventive HIV Vaccines Are Tested
Before being tested in humans, HIV vaccines are tested in labs and animals. A specific HIV vaccine could 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 I 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 II involves hundreds of healthy, HIV-negative volunteers and can last 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 III involves thousands of healthy, HIV-negative volunteers and can last 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.
The Hope for an HIV Vaccine
Despite the complex challenges HIV presents, many researchers are still hopeful about the prospects for an HIV vaccine. They point to several positive signs.
- Vaccines have been successful in protecting monkeys against a relative of HIV. Even when not completely protective, vaccines used in monkeys have allowed them to live much longer.
- In test tube studies, certain rare antibodies do work against HIV.
- Certain people remain uninfected by HIV after repeated exposure; others who do become infected either suffer no harm or remain unaffected for a decade or longer. This indicates that their immune systems are somehow effective against HIV. Finding out what's working so well in these cases has led to new drug development and could provide helpful clues in the development of a vaccine.
- There are also oral medications now being studied for preventing HIV. These drugs would need to be taken daily for those at high risk of acquiring the virus. For example, chronic drug users, or people who have unsafe sex or those with a spouse or partner who is HIV positive