California reported a drop in the rate of kindergarteners immunized against measles last year.
While California's childhood immunization rates are still high compared with the rest of the nation, the California Department of Public Health said 16 counties have fallen below the threshold for herd immunity against measles.
Experts say herd immunity is when enough people in a community have achieved protection against a virus that prevents a disease from spreading.
EdSource reports more than 96 percent of California kindergartners and transitional kindergartners were vaccinated against measles in the 2023-24 school year. That was down slightly from the year before.
Many of the lowest immunization rates can be found in Northern California, largely clustered around the Sacramento area.
