Although the recent outbreaks of Ebola appear to be waning, public health officials never know when it might flare up again. Recent tests with an experimental vaccine for Ebola strongly suggest that it is effective in preventing the infection from spreading.
The World Health Organization sponsored the trial on over 7,500 participants in Guinea—the site of the most recent outbreak. Researchers used a ring vaccination strategy that was used to eliminate smallpox. This process involves vaccinating all of the contacts of a person who has developed Ebola along with anybody in close contact with each individual.
The results suggest that the vaccine provides high protection as early as 10 days after vaccination. The researchers compared treatment groups who were vaccinated immediately against a control group of people vaccinated 21 days later. None of the people who were vaccinated immediately came down with Ebola, while 16 people in the delayed vaccination groups developed the disease.
In addition, this vaccination strategy appears to provide protection to people that could not be vaccinated, such as pregnant and breastfeeding women and children. People tolerated the vaccine well—one patient experienced an episode of fever related to the vaccine.
This particular candidate vaccine developed by the Public Health Agency of Canada is known as VSV-ZEBOV. The scientists genetically engineered the harmless virus vesicular stomatitis virus (VSV) by adding a gene for a surface protein on the Ebola virus. Thus, the vaccine does not contain any live Ebola virus.
Since the transmission of the Ebola virus is consistent across countries and regions, the researchers believe that the vaccine would be effective in other countries such as Sierra Leone and Liberia. However, it is still uncertain whether this vaccine could become licensed for widespread use, since more testing is required on the safety and efficacy of the vaccine.