Vaccine Research

What is a Vaccine?

 

A vaccine is a substance that is introduced into the body that teaches the immune system to detect and destroy pathogens - which are a particular virus, parasite or bacterium that cause disease.  ALL vaccines contain some harmless form or part of the pathogen they are trying to prevent.  Vaccines work through the adaptive immune response, which is a part of the immune system that learns to recognize and respond to certain pathogens.[1]  Think of it this way: a vaccine is like a drill instructor training your adaptive immune response system to recognize and fight harmful pathogens; a vaccine is your frontline defense in preventing the contraction of a disease such as HIV.

 

Types of Vaccines

 

• Whole-killed/ Whole-inactivated vaccines: (ex: the cholera and injectable polio vaccines).  These vaccines contain a specific virus or bacterium that has been killed and therefore stripped of its ability to infect humans.  These viruses and bacterium, while unable to infect the host body, do contain the necessary elements needed for recognition and response by the immune system against the targeted pathogen.

 

• This approach has not yet been used in the development of an HIV vaccine due to the small risk that the viruses harvested for experimentation may not have been killed or inactivated.

 

• Live attenuated vaccines: (ex: the measles vaccine and the oral vaccine against polio).  These vaccines use a form of the targeted pathogen that is highly unlikely to be harmful, but capable of multiplying.  This results in a vaccine that mimics the behavior of the targeted pathogen, giving the immune system an idea of what it would be up against in the event that a harmful pathogen were introduced.

 

• This approach has not been applied to the development of an AIDS vaccine because of the fear that attenuated HIV might revert to its disease-causing form

 

• Subunit vaccines: (ex: the seasonal flu and hepatitis B vaccines).  These vaccines are comprised of purified pieces of the pathogen - known as antigens- that create a vigorous immune response.

 

• This approach was used in the creation of the first AIDS vaccine candidate tested in humans.  The attempt failed however because the vaccine failed to induce protection against the HIV infection.

 

• DNA vaccines candidates: (ex: no vaccines of this kind have been approved for human use). These vaccines carry circles of DNA, called plasmids, which contain genes encoding purified antigens.  Human cells passively take up these plasmids and produce the antigens which teach the immune system to ward of the targeted pathogen.

 

• Several AIDS vaccine development efforts have employed this approach.

 

•  Recombinant Vector vaccine candidates: (ex: no vaccines of this kind have been approved for human use).  These vaccines are similar to DNA vaccines in that they introduce genes for specified antigens into the body, however these genes are inserted into a virus that actively infects human cells.  The viruses are safe to use because they do not ordinarily cause disease in humans, or they have been stripped of their ability to multiply.

 

• Several AIDS vaccines development efforts have employed this approach.[2]

 

Why a vaccine?

 

Since its discovery over 27 years ago, the human immunodeficiency virus (HIV), which has been identified as the cause of acquired immunodeficiency disorder (AIDS), has generated one of the most devastating pandemics ever recorded in human history. "More than 25 million people have died from HIV-related causes and roughly 33 million are living with HIV."[3] AIDS remains the fourth leading cause of death globally.  It is estimated that every day 7,400 people worldwide become infected with HIV.

 

The Vaccine Research Process

 

Before vaccines can be cleared for public distribution and use, they must pass through three trial phases.

 

1. Phase 1 is the first time during the development process when the   HIV vaccine is actually given to people.  These trials enroll between 20-100 HIV negative volunteers, and their primary goal is to determine the safety of the vaccine; more specifically if there are any side effects.  Also during this time a dosing and administration schedule can be formulated to determine the course needed to achieve optimal immune response.

 

2. Phase 2 trials are initiated once a safety baseline has been established.  In this phase the safety of the drug is further explored as is the development of a finalized dosing and administration schedule.

 

3. Phase 3 trials are the final step in the vaccine development process.  Only the most promising vaccines move into this phase where the goal is to determine the effectiveness of the vaccine in preventing HIV infection.  These trials involve thousands of volunteers and data indicating the drug's effectiveness among large groups of people is required for licensure application to the FDA.[4]

 

Vaccine Progress

 

Research in the area of development of an effect HIV/AIDS vaccine has been futile.  The vaccines that have been introduced either do not make it past the phase 1 trials or do not show promising enough success rates when tested amongst large groups. 

 

The first vaccine to successfully complete the phase 3 trial testing and emerge with hopeful results was the ALVAC-AIDSVAX trial conducted in Thailand.  On September 24, 2009 the Military HIV Research and the Thai Ministry of Public Health announced that a "prime-boost combination of two AIDS vaccine candidates showed partial efficacy producing a 31% success rate in preventing HIV infection" (www.iavi.org).    

 

For more information on AIDS vaccine research:

 

HIV Vaccine Trial Network

1-800-448-0440

www.hvtn.org

 

The HIV Vaccine Trials Network (HVTN) is an international collaboration of scientists and educators searching for an effective and safe HIV vaccine. The HVTN's mission is to facilitate the process of testing preventive vaccines against HIV/AIDS. Our organization conducts all phases of clinical trials, from evaluating experimental vaccines for safety and the ability to stimulate immune responses, to testing vaccine efficacy.

 

International AIDS Vaccine Initiative

+1 212-847-1111

110 William Street, Floor 27

New York, NY. 10038-3901

www.iavi.org

 

IAVI's mission is
to ensure the development of safe, effective, accessible, preventive HIV vaccines for use throughout the world.