Dr. Anthony Fauci, the nation’s top infectious disease expert, on Tuesday said he was “cautiously optimistic” that a vaccine to stop the coronavirus will be known “by this coming winter”.

“Hopefully by the time we get to this coming winter, we will know whether or not we have a safe and effective vaccine,” Fauci said, during a discussion sponsored by the Economic Club of Washington,

This would not be the last step in getting the vaccine ready, he noted. Once it is found that a vaccine is safe and effective on humans, the challenge will be to scale the vaccine up so there are enough doses for everyone, not just rich countries, Fauci said.

Asked about a report that researchers at Oxford University have developed a vaccine that has worked in monkeys, Fauci replied: “There are going to be a lot of candidates out there.”

“Hopefully we can move along rather rapidly to get an answer ‘are they are safe and effective?’,” Fauci said.

The doctor is sticking with his initial prediction, made in early April, that a COVID-19 vaccine could take 12 to 18 months to develop, test, and approve for human use. At the time, many experts said this timeline was unrealistic.

Fauci said he was “almost certain” the coronavirus will come back next winter.

“It is not going to disappear from the planet. Which means as we get into next season, in my mind, its inevitable that we will have a return of the virus,” Fauci said.