HIV Vaccine Trials Unit - University of Rochester

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Vaccines Past and Present

To learn more about HIV vaccine research studies in various Phases, visit: The Pipeline Project.

Past: More than 200 years ago, Edward Jenner, a country physician practicing in England, noted that milkmaids rarely suffered from pox, a disease that was known to kill 40% of those who contracted it. The milkmaids often did get cowpox, a related but far less serious disease, and those who did never became ill with smallpox. In an experiment that was to prove his theory, Jenner took a few drops of fluid from the skin sore of a woman who had cowpox and injected the fluid into the arm of a healthy young boy who had never had cowpox or smallpox. Six weeks later, Jenner injected the boy with fluid from a smallpox sore, but the boy remained healthy. This was the beginning of the first vaccine study.

Present: Today, things are much different. Vaccine volunteers are totally voluntary and go through an Informed Consent process. They are advised of the required visits to the clinic and are educated in advance about every detail of the study. No living or killed virus or pieces of virus are used in HIV vaccine studies. Modern biotechnology allows us to create synthetic vaccines that trick the immune system into thinking it is seeing the actual virus, when it is really just a cleverly disguised protein.

Types of Experimental Vaccines

Peptide Vaccine: made of tiny pieces of proteins from the HIV virus.

Recombinant Subunit Protein Vaccine: made of bigger pieces of proteins that are on the surface of the HIV virus. Examples of a recombinant subunit protein are gp120, gp140, or gp160 produced by genetic engineering.

Live Vector Vaccine: non-HIV viruses engineered to carry genes encoding HIV proteins. The genes are inserted into another vector, which carries them into the bodys cells. The genes in turn produce proteins that normally are found on the surface of the HIV virus. This type of vaccine most resembles virus but is not harmful. Many vaccines used today, like the smallpox vaccine, use this approach.

DNA Vaccine: uses copies of a small number of HIV genes which are inserted into pieces of DNA called plasmids. The HIV genes will produce proteins very similar to the ones from real HIV.

Vaccine Combination: uses any two vaccines, one after another, to create a stronger immune response. Often referred to as "prime-boost strategy."

Virus-like Particle Vaccine (pseudovirion vaccine): a non-infectious HIV look-alike that has one or more, but not all, HIV proteins.

Phases of research studies

There are three types or phases of vaccine trials that are done with people. However, before any human studies are started, every vaccine being researched must successfully complete rigorous testing in the laboratory and in animal studies.

Phase I studies are done to study side effects, if any, and to verify its safety. If the Phase I study finds that the drug is well tolerated and seems to stimulate an immune response, it may proceed to a Phase II study. A Phase I study typically requires a small number of participants.

Phase II studies look for the most effective dosage, as well as the best vaccination schedule for a promising vaccine candidate. In a Phase II study more people are given the vaccine to see how it works within the immune system and to continue to verify safety. A Phase II study can last a few years, and may involve hundreds of people.

Phase III studies test to see whether the vaccine actually protects people from being infected with HIV if their behavior exposed them to the virus after their vaccination. This phase may also help researchers to determine if those people who do become infected with the virus after vaccination take longer to develop AIDS.