Dr. Matt Willis, Marin County's Public Health Officer, attends one of the first pop-up senior COVID-19 vaccination clinics, set up at the Exhibit Hall of the Marin County Civic Center in March 2021. (Photo courtesy County of Marin)

COVID-19 cases in Marin County have tripled over the last six weeks due to the omicron subvariant BA.2, which is now the county’s dominant strain, local health officials said Wednesday.

The highly contagious variant has driven recent outbreaks in schools, long-term care facilities and jails and prisons, according to county officials.

COVID cases are rising across much of the Bay Area due to the variant, but Marin County has yet to see a commensurate rise in COVID-related hospitalizations or deaths, according to county Public Health Officer Dr. Matt Willis.

“We’re learning in real time about this new strain, and what it does and doesn’t do,” Willis said in a statement. “It’s very good at infecting people, including those who are vaccinated. But it’s not sending vaccinated people to the hospital.”

Experts estimate the BA.2 subvariant to be at least 25 percent more infectious than the main omicron variant that drove the state’s winter COVID surge.

However, residents who have completed their initial vaccination series and have received a booster reduce their risk of death by some 90 percent and also reduce their overall risk of being infected in general, according to county health officials.

As of Wednesday, 92.6 percent of all eligible county residents age 5 and up have completed their initial vaccination series.

“It’s increasingly likely most of us will have a date with COVID, if we haven’t yet,” Willis said. “The key is to be vaccinated and boosted before that happens, so we don’t end up seriously ill.”

Residents are encouraged to use a rapid at-home COVID test before attending gatherings with people from other households while virus levels remain high locally.

Information about COVID in Marin County can be found at https://coronavirus.marinhhs.org.