Low immunization rates for kindergartners at Lagunitas School District’s Open Classroom this year continue to run counter to a three-year countywide trend of increasing rates that county public health officials have hailed as a positive step toward preventing outbreaks of childhood disease. 

That’s despite the impending end of California’s personal belief exemptions, which next year will be outlawed as a means for kindergartners and seventh graders to avoid mandatory vaccinations due to a state law that took effect on Jan. 1.

This school year, 10 out of the elementary school’s 17 kindergarteners have filed personal belief exemptions. That nearly 60 percent opt-out rate starkly contrasts with Marin’s 6 percent rate, which dropped from 6.5 percent last year.

But incorrect data issued by the California Department of Public Health that logged zero personal belief exemptions for the Open Classroom could cast doubt over whether Marin County’s exemption numbers are accurate. Neither the county nor the school could say how the error had been made. Danielle Hiser, the county’s immunization coordinator, stopped short of celebrating the state’s data when the Light informed her of the mistake.

Historically, opt-out rates have been high at Open Classroom, where students participate in an alternative educational experience that relies on a philosophy of spontaneous and personalized learning, combines multiple grades in the same octagonal space and is steered by consensus decision-making between parents, staff and trustees.

This year’s data has left school officials wondering what may happen next year, when one of the few remaining ways for parents to avoid vaccines will be to homeschool their kids.

“It could have an impact on our enrollment if many families decide to leave,” said Laura Shain, the principal at the Lagunitas School District, which includes the Open Classroom program, a Montessori-based elementary program and a middle school. “We’re waiting to see what happens.” In the Montessori program, only one of 13 kindergarteners opted out of vaccination this year. (Two out of 10 kindergarteners at Bolinas-Stinson Elementary School filed personal belief exemptions and no kindergarteners at the three elementary schools in Shoreline Unified School District filed for exemptions.) 

Passed in July, Senate Bill 277 sparked a heated national debate about whether vaccines for diseases like measles and pertussis are truly safe for children, whether personal belief exemptions compromise public health and whether nixing personal belief exemptions was a violation of parents’ freedom of choice. 

Nowhere in West Marin were fears of vaccines better illustrated than the San Geronimo Valley, where a contingent  of parents have long taken the personal-belief road rather than give their children what they deem potentially harmful vaccines.

“There are ways of making safe vaccines,” said Michelle Veneziano, a Mill Valley osteopath whose daughter is a fifth grader at Open Classroom. “We’re just not doing it.”

Like many opposed to the new law, Dr. Veneziano fears that certain adjuvants added to vaccines—such as small amounts of aluminum and mercury—could pose a greater threat to infants than mainstream science would suggest. Also at issue is the standard schedule of vaccination; the vast majority of school-required vaccines are administered within the first few months and years of a child’s life.

Dr. Veneziano believes that parents of future kindergarteners who would have obtained personal belief exemptions may now look for their pediatricians to issue medical exemptions, which are still permitted under the new law. Medical exemptions are generally granted if a child has a family history of a medical condition that might make a vaccine dangerous. 

Since 2001, fewer than 10 kindergartners each year in Marin have had medical exemptions, aside from the 2006-07 school year. Even so, Marin County Public Health Officer Matt Willis conceded that the county could see those exemptions rise in coming years.

“I think it’s reasonable to assume that any change in medical exemptions might be linked to the new law, especially since there’s now an explicit allowance for a medical exemption that wasn’t there before,” he said. 

Dr. Willis is hopeful that parents and their physicians are going to have deeper conversations as a result of the law. “The fact that this is going to prompt longer and better-informed conversations between health care providers and the patients they serve is one of the primary benefits of this law,” he said. “Ultimately…we’re going to see fewer cases of disease, realized over many years as each new cohort of kindergarteners enters school.”

Others, however, are less conciliatory in their views toward parents who want to keep their kids off vaccines. “The absence of these diseases has created a false sense of safety that has caused some to rely on the herd community of vaccinated kids,” said Jeff Gimzek, a Petaluma designer who used to live in Lagunitas. “The actual danger of babies being infected with communicable and preventable diseases is being discarded.”

 Mr. Gimzek’s youngest daughter contracted the relatively mild skin disease impetigo from his eldest daughter, who brought it home from school. But her symptoms morphed into a painful and potentially life-threatening infection. The event caused him to recoil from the attitudes of neighbors who refused to vaccinate their kids. Eventually, his family left West Marin. “[Not vaccinating is] a privilege, essentially,” he said. “None of these people have had a child die from a communicable disease.”

But where Mr. Gimzek sees a privileged mindset, others describe a more educated outlook. Dr. Veneziano noted that more people have begun to take notice of studies questioning the safety of childhood vaccines, such one published by Israeli researchers in 2010 that posits a link between vaccine adjuvants—which increase the body’s immune response to a vaccine—and an autoimmune syndrome.

“The mandates have created the imperative for all of us to dive more deeply into the research and effectively address the very real concerns about the safety of these products,” Dr. Veneziano said. “I’m really glad that’s happening.”