Statistically speaking, the numbers are relatively small: The statewide percentage of California children entering kindergarten without having received all recommended vaccinations — because their parents have chosen not to vaccinate for personal reasons — is about 3 percent, according to the state Department of Public Health.

But not only has that percentage been climbing, the variation among schools is significant, and therein lies the problem, according to public health officials.

Preventing the spread of infectious diseases, like the pertussis (or whooping cough) epidemic of 2010, requires a herd immunity, public health officials say: The more people in a community immunized against the disease, the less likely it is to spread. And to achieve herd immunity against whooping cough, a 95 percent vaccination coverage reportedly is needed.

But some schools in California — including several in Davis — have immunization rates well below 95 percent for all diseases because parents are choosing not to vaccinate for personal reasons.

That prompted state lawmakers last year to pass legislation aimed at boosting immunization rates.

Under the new law, which takes effect in January, parents seeking a personal belief exemption from vaccinations must first visit their children’s health care practitioner for a discussion about vaccines and diseases.

Previously, parents simply checked a box saying they had exempted their children because of their personal beliefs; now they will need a health care practitioner’s signature as well.

“This bill is about explaining the value of vaccinations — both the benefits and risks — for an individual child and the community,” Gov. Jerry Brown said in signing the law. “Whether these are simple ‘information exchanges’ or more detailed discussions, they will be valuable even if a parent chooses not to vaccinate.”

Davis public health expert John Troidl says a simple conversation between doctor and parent can make a difference.

“A physician’s advice is typically taken very seriously,” Troidl said.

“The idea that you need to run this by your physician is well-founded in science,” Troidl said.

In signing the bill, Brown added a caveat that upset some in the public health sector — namely, that he is instructing the state Department of Public Health to add a separate religious exemption for which a health care practitioner’s signature will not be needed.

Critics said that could end up defeating the purpose of the bill, which is to increase immunizations, since parents who previously checked the personal beliefs box could simply check the religious box instead.

Troidl said he isn’t sure what kind of difference the religious exemption will make, but he is adamant about the importance of all children who are attending school with other children being vaccinated.

“I think every parent that wants to claim any exemption should home school,” he said. “Immune-compromised kids should not have to be exposed to disease-carriers because their parents don’t want to vaccinate them. There is no ethical reason for that risk.”

In Davis, the percentage of children who entered kindergarten without being up-to-date on their immunizations varied widely from school to school last year.

A full 100 percent of kindergartners were up to date at Redbud Montessori and Merryhill Elementary schools, according to data provided by the state Department of Public Health, while the public schools ranged from a high of 98 percent of kindergartners at Montgomery Elementary to a low of 87 percent at Birch Lane Elementary.

While only one child at Montgomery was exempted due to a parent’s personal beliefs, nine Birch Lane kindergartners were.

The lowest vaccination rate in Davis — and in all of Yolo County, in fact — was at Davis Waldorf School, where only 33 percent of kindergartners last year were up to date on vaccinations, according to the Public Health Department.

Waldorf has seen a steady decline in that number, from 47 percent in 2010-11 to 43 percent in 2011-12 to 33 percent last year, including 19 kindergartners whose parents claimed personal belief exemptions, according to the state.

Another 14 Waldorf kindergartners last year were listed as “conditional entrants,” meaning the child was not up-to-date on vaccinations and lacked either a personal belief or medical exemption at the time of enrollment.

Yolo County supervisors briefly discussed the low vaccination rates at their meeting on Tuesday.

“This does concern me that we have some school sites in the county where the percentage of people choosing to opt out is getting very high,” said Supervisor Don Saylor of Davis.

“I share your concern,” said his colleague, Supervisor Jim Provenza, who added, “There are immunizations that can’t be given to children under one year of age and yet their older siblings are not immunized and that puts the younger siblings at risk. We need to do everything we can here.”

County Health Director Jill Cook called the numbers concerning and added that the department is hopeful the new law will increase immunizations, but is unsure how the planned religious exemption will impact the law’s effectiveness.

Meanwhile, Cook reported improved immunization rates among seventh-graders in the county as a result of a new pertussis vaccine requirement that went into effect in the wake of the 2010 epidemic.

Most schools in the county reported between 93 and 100 percent of seventh-graders as up-to-date on vaccinations, with the exceptions being Waldorf, where 73 percent of seventh-graders were up to date and the Davis School for Independent Study, where 70 percent (or seven of the 10 seventh-graders enrolled) were fully immunized.

Unlike the personal belief exemption, medical exemptions for vaccines are extremely rare in Yolo County, with no seventh-graders in the county exempted for medical reasons last year and only one kindergartner.

— Reach Anne Ternus-Bellamy at [email protected] or 530-747-8051. Follow her on Twitter at @ATernusBellamy

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