Prepared by Chatu Yapa, Masters in Applied Epidemiology trainee, Health Protection NSW

For months, researchers have been working on a vaccine against Ebola Virus Disease (EVD) as part of continuing efforts to prevent the transmission of the virus in West Africa. Just this month (April 2015), the US Centers for Disease Control and Prevention in collaboration with the Sierra Leone Ministry of Health and the Sierra Leone College of Medicine and Allied Health Sciences have launched the STRIVE (Sierra Leone Trial to Introduce a Vaccine against Ebola) trial. This study aims to carry out a combined Phase 2 and 3 clinical trial to assess the safety and efficacy of a recombinant Vesicular Stomatitis Virus-Zaire Ebolavirus vaccine (rVSV-ZEBOV).

Phase 1 trials have already been conducted in Canada, Gabon, Germany, Kenya, Switzerland and the United States. These studies found that the vaccine did not produce any serious side effects in those who were vaccinated and scientists were able to determine a safe dose of the vaccine. However, they could not tell how much protection the vaccine would confer. The STRIVE trial will therefore help to answer this latter question by studying the vaccine in groups of people in various parts of Sierra Leone that have been affected by Ebola, thereby giving some guidance on the effectiveness of the vaccine.

For more information on the STRIVE trial, see ​Sierra Leone Trial to Introduce a Vaccine against Ebola (STRIVE) Q&A


  1. Regarding vaccines in general, what is the difference between vaccine efficacy and vaccine effectiveness?
  2. What are the types of epidemiological studies that are conducted to determine vaccine efficacy and effectiveness?
  3. Vaccine trials are conducted in different phases. What are the different phases in a clinical trial and what is their purpose?


Current as at: Monday 25 May 2015
Contact page owner: Health Protection NSW