Here, a laboratory robot was holding a well plate containing patients’ samples for SARS-CoV-2 antibody testing, using the CDC serologic test. (James Gathany/CDC 2020)

Contra Costa County health officials announced confirmation Monday of the county’s first cases of the omicron COVID-19 variant.

Three cases of the variant have been confirmed in the county, according to Contra Costa Health Services, with two of the three fully vaccinated.

None of the three had received a booster vaccine dose nor have they been hospitalized since testing positive for the virus.

County Health Officer Dr. Chris Farnitano said in a statement that it was only a matter of time when omicron would pop up in Contra Costa as it has in San Francisco, Santa Clara, Marin and Napa counties.

“We’ve been encouraging anyone who is eligible to get a booster dose of the Pfizer or Moderna vaccine to do so,” Farnitano said. “With today’s news and the holidays just around the corner, that message is even more important.”

Nearly 900,000 Contra Costa County residents have completed their initial vaccination series, equal to 77.4 percent of the county population.

However, only 34 percent of residents age 16 and up have received a booster dose to bolster their immune response.

All residents age 16 and up are eligible for a booster vaccine dose if they are at least six months past their second Pfizer or Moderna dose or at least two months past their single Johnson & Johnson dose.

While the three available vaccines remain highly effective at preventing serious COVID-19 illness and death, public health officials at all levels have argued that their protection begins to wane after several months, and that preemptively boosting a person’s immune response will maximize protection against existing and potential variants of the virus, which could continue to become more contagious and even circumvent vaccine protections.

“People who get the booster are far less likely to get gravely ill or be hospitalized,” Farnitano said. “That’s our wish for this holiday season.”

People can make an appointment to get tested for the virus or get vaccinated at https://www.coronavirus.cchealth.org.