Amid the largest nationwide measles outbreak in 17 years, vaccination rates in West Marin increased dramatically, though they still fall short of countywide rates and goals. This school year, the percentage of West Marin kindergartners who were vaccinated was 90 percent, below the 95 percent threshold believed to achieve community immunity. Yet that rate was a leap from 2015, when only 76 percent of kindergartners had received all of the required immunizations. The individual vaccination rates for the eight elementary schools in West Marin are unavailable due to their small size potentially making children identifiable, so it is unknown which schools have community immunity, and which are vulnerable. Out of 69 students, 62 were vaccinated, and another four planned to get vaccinated. The rising rate reflects a county-wide trend, with Marin at its highest-ever vaccination rate this year, at 94 percent. Marin County, which hasn’t seen a measles case since 2015, has been fortunate to avoid an outbreak, said Matt Willis, the county’s public health officer. Since it hasn’t attained community immunity—in which enough of the population is immune to a disease to make its spread unlikely—the threat of outbreak persists. “We’ve been at a risk for outbreaks, or clusters of cases, that we haven’t seen, and others around us have,” Dr. Willis said. Nationwide, this year has been especially bad for measles, with 1,044 cases since 2019 began, the largest number of cases since 1992. But Dr. Willis is encouraged. “I was surprised and heartened by the overall value of West Marin,” he said. “It helps us feel more secure that we’re less likely to see outbreaks in West Marin than we had been.” Historically, West Marin’s vaccination rates have been over 10 percent lower than in the rest of the county. But in 2015, it became harder to avoid vaccination when the state outlawed personal-belief exemptions, which 15 percent of families in West Marin had claimed. Since then, the number of medical exemptions has gone from zero to three in West Marin, and from eight to 80 countywide. A new bill moving through the California legislature, endorsed by Gov. Gavin Newsom, would require the use of a standardized medical exemption form, and require the state monitor doctors who give children exemptions. S.B. 276 would attempt to ensure that all physicians are acting on the best medical evidence, so that the only children receiving exemptions are the ones who truly need it. “Those situations are rare, but real,” Dr. Willis said. The Centers for Disease Control and Prevention has estimated that vaccines prevented more than 21 million hospitalizations and 732,000 deaths among children over a 20-year period. Even just one case of a vaccine-preventable disease, such as measles, would have serious consequences. First, the county would make sure the infected child was treated and quarantined. Then county staff would investigate everywhere the child had been and who they had been in contact with to make sure those people were not infected, and unvaccinated children would be barred from school for three weeks to prevent the disease’s further spread. “The choice for parents to vaccinate their child is really not just a choice for their own child, but for their friends, classmates and neighbors, as a matter of community responsibility,” Dr. Willis said.