National Guard Medic, Ross Davison, speaks to Greg Bryson, 63, after Davison administered a Johnson & Johnson COVID-19 vaccine to him at the drive-through vaccination site at Six Flags Hurricane Harbor (Waterworld) in Concord, Calif., on Wednesday March 31, 2021. (Ray Saint Germain/Bay City News)

California opened COVID-19 vaccine eligibility to all residents age 50 and older Thursday, the last step before making vaccines available to the state’s entire adult population later this month.

The expansion comes roughly three-and-a-half months after the first doses were shipped to local health departments and administered in the Bay Area and across the state.

According to state officials, roughly 7.2 million state residents are between age 50 and 64 and some 2.8 million of them have already received at least one dose by fitting into other, previously eligible categories like health care workers, educators and first responders.

The state is set to open vaccine eligibility to all state residents age 16 and older on April 15.

“We have an enormous opportunity in the next six to eight weeks to run the 100-yard dash, not the 90-yard dash,” Newsom said Thursday, acknowledging the concern of proliferating coronavirus variants.

“Let us not dream of regretting,” he said. “We’ve come so far together and we’re this close; 18-plus million vaccine doses have been administered in the state of California.”

Newsom, 53, celebrated the state’s eligibility change by receiving the one-dose vaccine developed by Janssen, the pharmaceutical subsidiary of Johnson & Johnson. He added that his wife, 46-year-old Jennifer Siebel Newsom, will receive the vaccine once she becomes eligible later this month.

Newsom cautioned that it will take several months to fully vaccinate every California resident seeking to receive a shot, due in part to continuing supply constraints.

State officials expect to receive roughly 2.4 million doses from the federal government next week. However, Newsom said, vaccination sites across the state still have the capacity to administer two times that number of doses per week.

“We’re confident we can deliver on that as long as the manufactured supply still comes into the state of California,” he said. “That’s the one criteria, that’s the one condition.”

Newsom also said the state is in the process of transferring operations of the mass vaccination sites at the Oakland Coliseum and California State University Los Angeles to Alameda County and the city of Los Angeles, respectively.

Since opening in February, the two sites have been operated by the Federal Emergency Management Agency, the Department of Defense and the state’s Office of Emergency Services and have been administering more than 7,500 doses per day.

“The two FEMA sites, combined, are less than 4 percent of our entire delivery system,” Newsom said. “So it’s not profound in terms of its impact, but it is an impact nonetheless and we try to get every dose we possibly can.”

Newsom encouraged all California residents to make a vaccination appointment as soon as they are eligible, saying it will hasten the state’s burgeoning recovery from the pandemic. Some 18 million vaccinations have already been administered across the state.

“I just encourage everyone 50 and over, do what I just did,” he said. “And I would encourage you, when you’re curious what’s the best vaccine to take, the best vaccine is the next one available.”

Residents who are eligible for the vaccine can visit or call (833) 422-4255 to schedule a vaccination appointment.