WASHINGTON (NEXSTAR) — With two pharmaceutical companies announcing in the last week that their COVID-19 vaccines in development are at least 90% effective, the federal government is preparing to get the shots out and people to buy in.

“There is light at the end of the tunnel,” Dr. Moncef Slaoui, the chief advisor of the Operation Warp Speed program to develop and distribute COVID-19 vaccines, said.

Pfizer announced last week its vaccine is about 90% effective and Moderna said Monday its is nearly 95% effective, which Slaoui called “really exciting.”

Slaoui said with his team ready to move as soon as the U.S. Food and Drug Administration starts issuing emergency approvals, it’s possible the entire U.S. population could be vaccinated by as early as June.

“We may be able to immunize up to 20 million people with two shots of the vaccine in December and then going forward from there, about 25 million every month,” he explained. “(Each) state will decide and tell us where to deliver those vaccines — for instance, into elderly nursing homes or into pharmacies.”

Millions of doses of the Pfizer and Moderna vaccines are already stockpiled, and Slaoui said he expects two additional vaccines in the pipeline will also be approved.

“Some may be best suited for frail, elderly people. Some may be best suited for babies. Some may be best suited for health care workers,” he said. “It’s by adding all these vaccines over time that we feel confident.”

The question now is whether Americans feel confident in getting the vaccines.

“We now have to convince people” that the science is solid, said Dr. Anthony Fauci, the nation’s top expert on infectious diseases.

“We’ve already crossed the line of efficacy. We’re there,” Fauci continued. “We’ve got to get people to be vaccinated.”

Slaoui agreed and said transparency will be key in getting people on board.

“We will make every data available,” Slaoui said. “We will explain to everyone how we went fast.”