President Biden on Friday urged older Americans, front-line workers and those with underlying health conditions who received a Pfizer coronavirus vaccine between January and March to get a booster shot.

“This week, as planned, we took a key step in protecting the vaccinated with booster shots, which our top government doctors believe provides the highest level of protection available to date,” Biden said. “The booster shot is free and easily accessible.”

Biden said up to 60 million Americans will soon be eligible, and 20 million Americans are eligible today.

Doses will be available nationwide at more than 80,000 locations, including more than 40,000 pharmacies, he said.

What about non-Pfizer recipients? They’re left waiting. While acknowledging most Americans who received a Pfizer shot are eligible for a booster, Biden urged people who received the Moderna and Johnson & Johnson vaccine to be patient.

“My message for you is this: You still have a high degree of protection. Our doctors and scientists are working day and night analyzing the data from those two organizations on whether and when you need a booster shot, and we’ll provide updates for you as the process moves ahead,” Biden said.