In the nearly three weeks since U.S. regulators cleared COVID-19 vaccines for kids ages 5-11, more than one in 10 of those children in California have rolled up their sleeves for the shots.

But those kids are concentrated in the state’s urban coastal counties. In the Bay Area, about one out of four kids in the biggest counties have already had their first shot, and an astounding 40% in Marin, once a hotbed of resistance to child vaccination. But far fewer in rural areas have been inoculated.

State health officials see vaccinating kids as key to blunting a feared winter infection surge, and some School districts, including Oakland, will require older students to be vaccinated to attend class starting in January.

“Vaccine administration to California children ages 5-11 is off to a strong start, with more than 300,000 first doses administered in the first two weeks,” the California Department of Public Health said. “We are encouraged by this progress but continue to urge families — from young kids to grandparents — to get vaccinated, complete their vaccination series, and get a booster once eligible to strengthen their protection against COVID-19 in time for the holidays.”

It’s hard to say how California compares nationally, as the U.S. Centers for Disease Control and Prevention as of Friday was still in the process of reporting figures for that age group by state. California as of Friday reported 11% of children 5-11 having a first shot of the vaccine. Illinois reported 12.4% with at least one shot in that age group, and Texas 7.4%.

Among California’s five most populous counties — all outside the Bay Area — none reported vaccination rates for kids 5-11 that were higher than the state’s 11% average. Los Angeles reported 10% had gotten a shot.

By contrast, Marin County was the runaway leader with 40.4% of kids ages 5-11 having at least one of the two Pfizer shots, which are given three weeks apart at a third of the dosage for teens and adults.

Marin County Health Officer Dr. Matt Willis credited the high numbers to strong public interest in the vaccines and collaboration with local schools to make them readily available.

“It was a super high priority for us,” Willis said. “There was a lot of excitement built up in Marin for when our kids were finally eligible for vaccination, and we did a lot of preparation.”

The five most populous Bay Area counties have vaccination rates at least twice those in the big Southern California counties: 26.9% in San Francisco, 24.6% in Alameda, 24.5% in Santa Clara, 22% in San Mateo and 21.5% in Contra Costa.

In Santa Clara County, vaccine officer Dr. Marty Fenstersheib said child immunizations are shifting from mass vaccination sites to school clinics, but interest has remained steady.

“We’ve heard for a long time a lot of parents were excited about the opportunity to get their young kids vaccinated,” Fenstersheib said.

It’s a different story in most of California’s rural interior, where many counties had vaccination rates for 5- to 11-year-olds under 5%.

Gov. Gavin Newsom on Tuesday visited Kings County, where the vaccination rate Friday stood at 2.7%, to promote vaccines at a school in Avenal. He bemoaned what he called disinformation about the safety of the shots, adding that he’s had the vaccine and a booster shot and that his 12-year-old had been vaccinated a few weeks ago and his 9-year-old was getting the jab later that day.

“In order to attend schools like this you’ve had to get 10 vaccinations,” Newsom told reporters, noting the array of immunizations for diseases like chickenpox and measles that the state already requires for public school attendance. “Vaccinations have been around for a century. They’re safe.”

Newsom announced Oct. 1 that California will add the COVID-19 vaccine to the list of required immunizations to attend schools once they are fully approved by federal regulators for school-aged children.

The Food and Drug Administration has fully approved Pfizer’s vaccine for ages 16 and older, but has so far authorized it only for emergency use in kids 5-15. Given the expected federal approval timeline, Newsom said the statewide requirement for children, which is to roll out separately for primary and secondary grades, likely won’t begin until the start of the 2022-23 school year.

Without new legislation, personal belief exemptions, which lawmakers eliminated in 2015 for other school vaccines, would be allowed.

Despite the statewide timeframe, several California school districts have moved ahead with their own COVID-19 requirement for students to attend class in person, with many taking effect in January, including at Los Angeles Unified and Oakland Unified. But those mandates apply to students 12 and older. About 69% of students 12-17 statewide have had at least one shot.

Willis said Marin County schools haven’t needed the threat of vaccine mandates to get so many of their kids vaccinated, a notable shift given that the county had one of the lowest overall immunization rates in its schools when the state eliminated personal belief exemptions in 2015.

“The culture has changed in Marin around vaccinations,” Willis said. “Our strategy has been to do everything we can to educate the community. It’s been more the carrot than the stick so far.”

Now, parents are flocking to school clinics to vaccinate their kids, sites where there’s music, balloons and “comfort dogs” to “make it a child-friendly experience.”

“It feels like a celebration at these vaccination sites,” Willis said.