Even in a best-case scenario, the country may be six months or more away from widespread inoculations. And we may not be in a best-case scenario, which could require policymakers and the public to develop plans for the long haul.

“So far the story of the vaccine development seems to be that none of the things that could have gone wrong have gone wrong,” Bergstrom said. “That doesn’t mean we’re home free by any means.”

If there’s a Plan B, it’s not clear what it is at the moment. The White House and its allies in Congress are struggling to negotiate even the next temporary relief bill, and Trump has repeatedly speculated that the U.S. will soon find a vaccine or cure, or that the virus will “disappear” on its own.

That has some people nervous. Ken Frazier, CEO of the pharmaceutical giant Merck, recently warned that anyone hyping a medical breakthrough before 2021 was doing a “grave disservice to the public” given the inherent challenges of developing and administering a vaccine.