BRUSSELS, June 25 (Reuters) - It is not certain that scientists will be able to create an effective vaccine against the coronavirus that has caused the COVID-19 pandemic, but it could take a year before one were to be invented, the head of the World Health Organization said.

Speaking by video-conference to deputies from the European Parliament's health committee, Tedros Adhanom Ghebreyesus said that if such a vaccine became a reality, it should become a public good available to all.

"It would be very difficult to say for sure that we will have a vaccine," Tedros said. "We never had a vaccine for a coronavirus. So this will be, when discovered, hoping that it will be discovered, it will be the first one," he said.

He said the WHO had already more than a 100 candidates for a vaccine of which one was at an advanced stage of development.

"Hoping that there will be a vaccine, the estimate is we may have a vaccine within one year. If accelerated, it could be even less than that, but by a couple of months. That's what scientists are saying," he said.