Measles Vaccine Gaps Uncovered in Contra Costa County and Neighboring Areas

Even though Northern California usually boasts impressively high measles‑vaccine rates, a recent Kaiser Permanente study shows the picture isn’t uniform. Researchers drilled down into the records of 7‑year‑old members and uncovered seven distinct clusters where the coverage slipped under the level needed for herd immunity.

Those clusters stretch across eight counties—including large swaths of Sonoma, a slice of Napa, and several tracts in Contra Costa—covering 242 census blocks and about 10.8% of the children examined (roughly 25,800 kids). The combined vaccination rate in those zones was 94.6%, just shy of the 95% benchmark health officials cite as the safety net against a measles outbreak.

The findings, published in JAMA Network Open on July 30, are meant to give local health departments a map of where vulnerability is highest. With measles making a stubborn comeback—58 cases reported in the first quarter of 2024 alone, 93% linked to international travel—identifying these gaps is more than academic. California saw its case tally match the entire previous year’s total by March, and exposure alerts have popped up at places like UC Davis Medical Center and an Alameda County restaurant.

In the East Bay, Contra Costa Health warned residents after a measles patient shopped in Lafayette and Walnut Creek in late 2025, touching stores such as Macy’s, Anthropologie and the Apple Store while contagious. Meanwhile, Napa County logged its first resident case since 2012, and wastewater testing even caught the virus’s genetic signature in the city’s sewers this spring.

The CDC still recommends two doses of the MMR vaccine—first between 12‑15 months, second between ages 4‑6 or before school starts—and advises anyone traveling abroad to be up to date, even as early as six months old. Remember, measles spreads like wildfire: nine out of ten unvaccinated people nearby can catch it from a single infected person, and the virus can linger in the air or on surfaces for up to two hours.

If you want to stay informed about local measles activity, keep an eye on your county health department’s alerts. Simple steps—checking vaccination records, getting that second dose on time, and staying aware of travel‑related risks—can keep the community safe.