• How do vaccines work?
  • What are HIV vaccine trials?

UNDERSTANDING HIV/AIDS VACCINES – http://www.afroaidsinfo.org

“One of the best hopes of controlling the HIV/AIDS epidemic is to develop a safe, affordable and effective vaccine (SAAVI,2010). It is an important part of the South African Government’s HIV/AIDS and STI Strategic Plan. Find out what a vaccine is, how it works and understand the importance of a clinical trial.


vaccine protects your body from diseases that make you very sick or even kill you. They also boost your natural defence system which is called your immune system. Vaccines usually come in the form of an injection, often called “shots” or “immunisations” (PHAC, 2012; SAAVI, 2010).

How do vaccines work? (PHAC, 2012)

  • Some vaccines contain small amounts of germs that are weak or dead.
  • These small doses of germs cause your immune system to build antibodiesto fight off the disease. Antibodies help trap and  kill germs that could lead to the disease
  • Your body can make antibodies in two ways: When you have been ill with a disease or when injected with a vaccine. A vaccine is a safer way to develop antibodies because you will not get sick.
  • When you get a vaccine, the antibodies stay with you for a very long time. The antibodies do not forget how to fight off the germ that caused the disease.
  • For some diseases, the antibodies need a reminder which  is when you need a booster shot.

What are HIV vaccine trials?

HIV vaccine trials are important studies where scientists try to stop the spread of HIV because the task of vaccines is to provide protection against infections or diseases. Scientists test what happens when vaccines are given to people. The HIV Vaccine Trails Network (HVTN) is an international team of scientists looking for a safe HIV vaccine. There are always new trials taking place. These are the different phases of a trial (HVTN, 2013):

  1. Pre-clinical trials: During this phase, animals such as mice and rabbits may be used. This is not always done, because people do not have the same immune system as animals. These studies are conducted in laboratories, and not clinics, which is why they are called preclinical trials.
  2. Phase 1 trials: Phase 1 only uses a small group of HIV-negative people (20 – 100) and only tests the safety of the vaccine.  This lasts 12 – 18 months
  3. Phase 2 trials: This includes hundreds of people with high and low risk of getting HIV. During this phase, it is decided on the right dose. Phase 2 can last for two or more years.
  4. Phase 3: This includes a few thousand people at high  risk who volunteer to see if the vaccine works to prevent HIV-infection.   This can last between 3 – 5 years.

The availability of a safe and effective vaccine would mean that more people would be protected from HIV infection than if other prevention plans were used (WHO, 2013).

Figure 2: Example of an injectable vaccine

Since large numbers of participants are needed in vaccine trials, people would be more willing to participate if they understood how it works. Understanding would also help to educate other potential trial participants in their communities. As a volunteer, it is important to understand that people cannot become HIV-infected by receiving an experimental vaccine during the trials (HVTN, 2013).

The following link, giving access to the South African AIDS Vaccine Initiative, provides questions and answers on “The background to HIV vaccines”. This four page document aimed at the public includes illustrations and intends to improve public understanding of HIV, how the immune system works and how a vaccine could be used to destroy the virus to prevent HIV-transmission (SAAVI, 2010).

Visit the link above to learn and share this document with friends and family who are HIV-positive or a caregiver of HIV-positive people.”

 Jodilee Erasmus (B.Soc Sci) 
Reviewed by: 
Hendra van Zyl (MPH) and Michelle Moorhouse (MBBCh, DA)
Date: October 2013
Preferred citation: Erasmus, J. (2013) Understanding HIV/AIDS vaccines, AfroAIDSinfo. Issue 13 no. 10, Public (Open access)
Last updated: 1 October, 2013


Posted by Stella Heuer 8 October 2013