Tens of millions more Americans would become eligible if authorization is granted for the Pfizer-BioNtech booster for anyone age 18 and older.

According to NPR, Many U.S. adults have already been eligible for a booster. In fact, eligibility is already so broad that something like two out of every three fully vaccinated people already meet the criteria for getting a booster.

Some states such as California have already made boosters eligible for all adults. Even so, millions don’t yet qualify and will be watching for the possible booster authorization this week.

Scientists are still debating the issue of whether all people truly need a booster right now. Some experts say open eligibility for boosters is vital to reinforce people’s immunity as much as possible from such a deadly and disabling illness.

But others experts argue the focus should instead be on getting unvaccinated people in the U.S. and around the world their first shots.

A new licensing deal from drug manufacturer Pfizer will soon assist in the fight against the pandemic in counties with low vaccination rates and limited vaccine access.