The experimental Ebola vaccine designed by Canadian scientists seems to work, the interim results of a trial in Guinea suggest.

If proven effective, the vaccine could be "a game changer," said Dr. Margaret Chan, director general of the World Health Organization, which sponsored the trial.

The interim findings were published online Friday in the medical journal The Lancet.

The findings so far are persuasive, Dr. Marie-Paule Kieny, a senior author of the trial, told reporters from Geneva.

"The data so far shows that none of the 2,014 persons vaccinated developed Ebola virus disease after 10 days after vaccination," said Kieny, who oversees research and development related to Ebola at WHO.

The search for a vaccine was spurred by the current Ebola outbreak in West Africa , which has killed more than 11,000 people in Guinea, Sierra Leone and Liberia since the epidemic began in Guinea in December 2013.

Marie Paule Kieny, World Health Organization assistant director general for health systems and innovation, says early results from a clinical trial of an experimental Ebola vaccine suggest it works quickly and it works well. (Denis Balibouse/Reuters)

The vaccine, known as rVSV-ZEBOV, was tested on more than 4,000 people who had been in close contact with a confirmed Ebola case in Guinea.

Of those who received the vaccine within 10 days of being identified as an Ebola contact, there were no cases of the disease. That compared with 16 cases in more than 3,500 people who received the the shot after 10 days.

"It suggests it works, it works pretty quickly and it works well," said Kieny.

More conclusive evidence is needed and trials will continue, WHO tweeted.

Dr. Joanne Liu, international president of Doctors Without Borders, said more research is needed to understand exactly how the vaccine protects and how long the protection lasts.

"But this is a first ray of hope: an effective vaccine could be a game changer to finally put an end to the outbreak which is still not under control in West Africa," Liu said on Facebook.

In a "ring vaccination trial," rings of contacts around Ebola cases are identified and randomly vaccinated either immediately or after 21 days. The time lag avoids the need to use a placebo.

Doctors used the same strategy of vaccinating those at greatest risk first to eradicate smallpox in the 1970s.

'Amazing accomplishment'

Given the positive results, Kieny told reporters that the delayed vaccination arm of trial will end and all contacts will be vaccinated immediately. Children and teens will also now likely receive it.

Kieny added Sierra Leone's government will now need to decide if it also wants to use the ring vaccination approach.

Dr. Alison McGeer, director of infection control at Toronto's Mount Sinai Hospital, made multiple visits to help control the outbreak in Liberia between October 2014 and January 2015. She's excited by the early data on the vaccine.

"The amazing thing about it is the amount of progress that has been made in vaccine development in a short period of time," McGeer said.

"We needed to do better, which is true. But still, this is the first Ebola vaccine trial.… This is the first time we've ever done a vaccine trial in the middle of an outbreak. This is the first time we've ever done a vaccine trial in Guinea. There's a whole lineup of check boxes of things that are close to impossible that this this the first of. It is just an amazing accomplishment."

Dr. Andrew Simor, chief of microbiology and infectious diseases at Sunnybrook Hospital in Toronto, worked in Sierra Leone in January training Ebola-fighting crews.

Simor agreed with Chan's assessment of the vaccine as a game changer.

"Had this vaccine been available a year ago, I think it had the potential to save literally thousands of lives," Simor said.

The vaccine was developed at the Public Health Agency of Canada's National Microbiology Laboratory in Winnipeg under the direction of Dr. Gary Kobinger.

Simor said the scientific work at the Public Health Agency of Canada was critical because researchers recognized the fragment of the Ebola virus most likely to spark a protective immune response, the first step in developing a vaccine.

"We are proud of the work done by Public Health Agency of Canada scientists that led to the development of the vaccine and hope that it can be used as a global resource to help save lives and end the outbreak in West Africa," Health Minister Rona Ambrose said in an email.

The vaccine was originally licensed to NewLink Genetics and Merck & Co. has an exclusive worldwide licensing agreement to research, develop, manufacture and distribute it.

The trial is also funded by the: