With the United States moving closer to giving booster shots of Pfizer’s COVID-19 vaccine to certain high-risk Americans, California officials said millions are expected to become eligible for third doses in the state — and they’re prepared to administer them.

Roughly 6.5 million Californians over the age of 65 — many of whom got Pfizer’s vaccine — are approved by the FDA to get a third shot, California Health and Human Services Secretary Dr. Mark Ghaly said in a media briefing Thursday.

The state also anticipates seeing an estimated 170,000 to 250,000 Californians coming forward to get the additional shot in the coming weeks because they’re at higher risk of COVID-19, according to Ghaly.

Officials said the state will need to ramp up its vaccinations to keep up with the expected demand.

The Food and Drug Administration on Thursday authorized booster doses for Americans who are 65 and older, people with underlying health conditions and those in jobs that put them at risk for COVID-19. Next, the Centers for Disease Control and Prevention will make its own, more specific recommendations about who should get the extra shots and when.

While specifics haven’t been announced, an FDA official told the Associated Press that the agency’s authorization would allow boosters for health care workers, teachers, grocery workers and those in prisons or homeless shelters.

Ghaly said California is working with local authorities and health care providers to make sure the state is ready to immediately begin administering booster doses to eligible Californians once recommendations are made.

The state’s MyTurn vaccine platform is ready to launch its booster appointment finder to help people find vaccine appointments near them, officials sad.

And Californians eligible for a booster will also get text message alerts from the platform.

Officials are working to make sure the state can meet demand for boosters, while also readying to administer vaccines to children under the age of 12 — who are expected to become eligible as early as next month, according to Gov. Gavin Newsom’s office.

Estimates are that California may need to administer an additional 63 million doses by the end of 2022. That not only includes those who need boosters, but also children younger than 12 who are not yet eligible to receive the shots, and millions of already eligible Californians who remain unvaccinated.

“Modeling indicates that vaccine administration capacity will need to ramp up over the next 4-12 weeks,” state officials say in a vaccine distribution plan released Thursday.

Currently, California providers are giving out between 60,000 and 150,000 vaccine doses per day. That number will need to go up to about 370,000 doses per day in late December if officials decide boosters should come after eight months, or to 600,000 doses a day in October if they go with a six-month booster plan.

One challenge to delivering booster vaccinations is that the long-term care federal pharmacy partnership has ended, and there won’t be federal staffing resources available to help with inoculating the older residents.

Also, providers have scaled back vaccination operations and will need to figure out if they will ramp back up, state officials said.

“We fully support our federal partners’ determination to provide boosters, and California has built the necessary infrastructure to mobilize such vaccine distribution – all to help protect the health and well-being of Californians,” Newsom said in a statement.

While the initial rollout of COVID-19 vaccines in California was rocky and marked by vaccine supply shortages and scarce appointments, Ghaly says the state is capable of meeting the demand for the third doses.

“This time around, we have a lot of capacity built up — over 7,000 providers across the state,” Ghaly said.