Walgreens and Rite Aid have begun giving out second booster shots along with Santa Clara and Contra Costa counties since federal health officials Tuesday greenlighted them for all Americans who are 50 and older.

Second boosters are also available to anyone who initially had Johnson & Johnson's one-shot vaccine and those with compromised immunity.

Santa Clara and Contra Costa counties began giving out the second booster shots shortly after Tuesday's announcement by the Food and Drug Administration and Centers for Disease Control and Prevention.

Contra Costa County said second boosters are now available at county-run vaccination clinics.

Walgreens said it would begin taking walk-in appointments Wednesday through Friday as store capacity allows, and that online appointment scheduling will be available via the Walgreens app or online at Walgreens.com/ScheduleVaccine starting Friday.

Rite Aid said Wednesday that second COVID-19 boosters are now available at all of its locations for eligible individuals who either may walk in immediately or schedule an appointment at www.riteaid.com/pharmacy/scheduler.

CVS said eligible patients "soon" will be able to schedule an additional dose four months after their initial booster at CVS.com, MinuteClinic.com or through the CVS Pharmacy app. Same-day or walk-in vaccination appointments may be possible, CVS said, but subject to local demand.

Kaiser Permanente and Sutter Health both said Wednesday they were awaiting further guidance from federal, state and local officials.

President Biden spoke about efforts to battle the virus Wednesday before rolling up his sleeve to receive his second booster.

"It didn't hurt a bit," Biden said. "We know boosters are critical to providing an additional layer of protection. Those who are 50 and older as well as those who are immunocompromised can now get even more protection than they have from the first doses."

Biden announced a new COVID.gov website, which he said would serve as a "one-stop shop where anyone in America can find what they need to navigate the virus."

"Free vaccines and boosters, free at-home tests, high-quality tests, and for the latest information about the spread of COVID-19 in your community, you can get that immediately," Biden continued. "The bottom line: No longer will Americans have to scour the internet to find vaccines, treatments tests or masks, it's all there."

At this time, vaccine clinics hosted in partnership with Solano Public Health offer eligible boosters and additional doses and can be found here: http://www.solanocounty.com/depts/ph/coronavirus_links/covid_19_vaccines.asp

At this time, the California Department of Public Health has not updated its guidance to align with the federal health officials announcement from earlier this week, according to the Solano County Health Department office.

"Solano County Public Health continues to align with state recommendations for booster doses and types of vaccine community members should receive," said an email sent to the Times-Herald.

The California Department of Public Health's guidance on boosters and additional doses can be found here: https://covid19.ca.gov/vaccines/#Booster-shots-and-additional-doses

Individuals may also check with their healthcare provider for additional information and vaccine clinics, Solano County officials said. Qualifying individuals can also schedule an appointment at their nearest pharmacy that administers booster doses. These include Walmart pharmacy, Safeway pharmacy, CVS, Rite Aid, and Walgreens, Solano officials added.

-- The Times-Herald contributed to this report.