Singapore: In a recent interim study published in the Lancet medical journal, Merck's Ebola vaccine was found to be "highly effective," in clinical trials. The vaccine was tested on more than 4,000 people who were in close contact with Ebola patients in the African nation of Guinea.

The vaccine was developed by the Public Health Agency of Canada and licensed to NewLink Genetics. Last year, Merck had inked an agreement to research, develop and distribute the vaccine. The clinical trial of the vaccine began on March 23.

In the trial, researchers vaccinated anyone in the close circle of contacts of a newly infected person, targeting those most likely to get the disease after a new case. Volunteers were protected against the Ebola virus within six to ten days of vaccination.

Describing it as a milestone towards Ebola relief, Ms Margaret Chan, director-general of the World Health Organization, said in a statement, "This is an extremely promising development. An effective vaccine will be another very important tool for both current and future Ebola outbreaks."