National Guard Medic, Ross Davison, administers a Johnson & Johnson COVID-19 vaccine to Laurie Pearce, 52, 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)

Contra Costa County officials Wednesday celebrated the opening of the county’s first mass vaccination site, which will eventually have the capacity to administer some 15,000 COVID-19 vaccine doses per week.

The drive-thru vaccination site at Six Flags Hurricane Harbor in Concord opened Tuesday after the county’s vaccination supply swelled enough to open vaccination eligibility to all residents and people who work in the county who are age 16 and older.

County officials had planned for several weeks to open a mass vaccination site, but hadn’t had enough available doses to use outside of smaller vaccination clinics, retail pharmacies and multi-county health care entities.

“We promised our community we would open a large-scale vaccination site once we had enough vaccine,” county Deputy Health Officer and COVID-19 Operations Chief Dr. Ori Tzvieli said Wednesday morning at the water park. “That day has come.”

Contra Costa County is operating the vaccination site in collaboration with Kaiser Permanente and the National Guard.

“The goal of this site is to continue to add to the broader solution for vaccine access and increasing capacity in Contra Costa County,” said Chris Boyd, Kaiser’s senior vice president and area manager for the Diablo Valley. “The health and safety of our members and the communities we serve is our top priority.”

Tzvieli said the county has been inundated with requests for vaccine appointments since opening them to all adult residents on Tuesday.

The county received some 30,000 requests within the first 24 hours of opening eligibility to the roughly 375,000 county residents between the ages of 16 and 49 that have yet to be vaccinated.

“We had appointments that were at risk of not being filled and we wanted to fill them,” Tzvieli said. “We knew we would get a deluge of interest, but we also knew that we had more confidence in our vaccine supply coming through that we’ll be able to have more and more appointments.”

Roughly 663,000 vaccine doses have been administered countywide, according to Contra Costa Health Services. Nearly a quarter of a million residents have been fully vaccinated, either with two doses of the vaccines developed by Pfizer and Moderna or one dose of the vaccine developed by Johnson & Johnson.

County officials initially set a goal of administering 1 million doses by July 4, but recently moved that deadline up to May 31 following ahead-of-schedule vaccination progress.

Cars line up to receive a Johnson & Johnson COVID-19 vaccine at the drive-through vaccination site at Six Flags Hurricane Harbor (Waterworld) in Concord, Calif., on Wednesday March 31, 2021. The vaccine is available to people who live or work in Contra Costa County and are 16 years or older.(Ray Saint Germain/Bay City News)

Eligible county residents can sign up for a vaccine appointment at https://www.coronavirus.cchealth.org or by calling (833) 829-2626.

County officials noted that eligibility for residents ages 16-49 is only in effect at county-operated vaccination sites and does not apply to retail pharmacies like CVS and Walgreens, which will open vaccine eligibility to all adults in accordance with the state on April 15.

“The day we gave the first vaccine in our county, we declared that getting everyone protected was our top priority,” county Board of Supervisors Chair Diane Burgis said. “We haven’t strayed from that goal. Today, those efforts are getting a major shot in the arm.”

Tzvieli said he was confident that the county will meet its Memorial Day deadline for 1 million administered doses and could even do so earlier than the end of May.

“These vaccines are our strongest tools to end the pandemic,” Tzvieli said. “Today is a good day.”