The proposal to start ramping up production while the candidate is still in a clinical trial is a risky step for a manufacturer, which would have to start assembling raw materials to make a vaccine without knowing whether it would work.

But the plan would make sure a vaccine is ready for patients if Covid-19, the disease caused by the new coronavirus, comes back next year, Fauci, the director of the National Institute of Allergy and Infectious Disease in the National Institutes of Health, said Thursday at a White House press conference.

The vaccine candidate, which is being developed by scientists at Fauci’s institute, entered into a phase I clinical trial earlier this month, which means it’s being introduced into the human body for the first time to a small group of patients. It’s the larger phase II trials that demonstrate whether the potential vaccine is safe and works well enough to warrant Food and Drug Administration approval.

“When I go into phase II, I want to find somebody that’s going to make it,” Fauci said. “Because once you know it works, you can’t say, ‘Great it works. Now give me another six months to produce it.’ So we’re working with a variety of companies to take that risk.”