The director of the Johns Hopkins Center for Health Security said Sunday that Americans should not “bank” on a coronavirus vaccine by year’s end, but said it is a possibility in a best-case scenario.

Asked by NBC’s Chuck Todd on “Meet the Press” whether the frequently cited timeline of 12-18 months is “realistic,” Tom Inglesby said that “coming into this year, I would have said it was completely unrealistic,” but added it “is far from a sure thing.”

However, he said that “given that there are now 110 vaccine projects going on around the world, that all the major vaccine companies in the world are working on this in some way, and given that [National Institute of Allergy and Infectious Diseases Director] Tony Fauci and [former GlaxoSmithKline vaccine chief] Moncef Slaoui are now leading figures in the U.S. in this project and they both believe it’s possible, I think it is possible.”

“[E]verything would have to break in the right way. And there are many ways that it might not work. So, I don’t think we should bank on it,” he added. “But we should hold out some level of hope that if everything goes in the right direction, we could possibly be seeing a vaccine by the end of the year.”

Inglesby said it is “difficult to predict” how the next three months will work, but said “the future really is in our hands” and largely dependent on the extent to which people avoid large gatherings and practice social distancing.

“I’m hopeful that states will be able to, to control their outbreaks. We also need to have very strong contact tracing efforts around the country,” he added. “That’s what, that’s what countries around the world have used with a lot of success, so if you get a case you investigate it quickly, you make sure all those contacts are safely quarantined, and we keep control that way. I think we shouldn’t think of this as kind of starting and stopping and this is over. This is a longer-term process.”