HIV drugs have vastly improved the quality of life for many of people living with HIV and AIDS, but they can't yet cure the infection. Someone at high risk for HIV can take a pill to help prevent an infection, but they'll have to take one every day. This method, called PrEP, isn't 100% effective.
That's why researchers are working hard to create an HIV vaccine.
A vaccine prevents or controls a specific infection by training the body's immune system to fight it. Over the years, scientists have made vaccines for diseases including typhoid, measles, influenza, and smallpox. More money has been spent on finding an HIV vaccine than on any other in history.
Although it's been decades since the discovery of the virus, we still don't have a vaccine for it. Why? Developing one is almost always a long process. It took 47 years to come up with a polio vaccine!
An HIV vaccine is even more difficult because:
- The HIV virus makes copies of itself very quickly.
- Many types of HIV exist, and new types keep forming.
- HIV has clever ways of "outwitting" the immune system.
Scientists are still trying to figure out specifically how the immune system could prevent HIV infection. Despite the complex challenges, many researchers are hopeful about the prospects of an HIV vaccine.
Two Kinds of Vaccines
Preventive vaccines train your immune system to "recognize" and fight off HIV before the virus causes a long-term infection and makes you sick. They're for people who are HIV-negative. Someday, a vaccine may be able to prevent HIV infection in all, most, or some people.
Because they don't contain any live virus, these vaccines can't give you HIV. But they might prompt your immune system to make antibodies that would show up on a blood test and give you a false positive result.
Therapeutic vaccines help control infection and delay the progression of the disease. They work by ramping up your immune system to find and kill HIV-infected cells and by preventing or limiting HIV from making copies of itself. They're being tested in people who are already HIV-positive but who have healthy immune systems.
Vaccine Testing and Clinical Trials
First, HIV vaccines are tested in labs and animals. Then, a single HIV vaccine could take years of testing in humans before it would be OK for the public.
A vaccine to prevent HIV typically goes through three phases of clinical trials to test its safety and effectiveness. People in all three phases are supposed to keep practicing safe sex. They're not deliberately exposed to HIV after they've been vaccinated.
Each phase must go well in order to move on to the next one.
- Phase I lasts between 12 and 18 months. Small numbers of healthy, HIV-negative volunteers help researchers test the safety and figure out best doses.
- Phase II can last up to 2 years. Hundreds of healthy, HIV-negative volunteers help researchers to refine dosing and test how well the immune system responds.
- Phase III can last 3 to 4 years with thousands of healthy, HIV-negative volunteers.
Certain people don't get infected by HIV, even after they've been exposed to it more than once. Others who do get infected don't seem to be affected for a decade or longer. These examples suggest that some immune systems are able to fight HIV.
In test tube studies, rare antibodies do work against HIV.
Vaccines have successfully protected monkeys against a relative of HIV. Even when the vaccines haven't completely protected the monkeys, they allowed them to live much longer.
Finding out what's working in these cases could provide clues for the development of an HIV vaccine.