At Roseland Elementary School in Santa Rosa, all but one of the 118 kids who entered kindergarten in 2009 were fully immunized, according to the latest state records.

With an "up-to-date" immunization rate of 99 percent, the school shows the benefit of an on-site children's clinic that has been aggressively giving children the Tdap pertussis booster, meningococcal vaccine and varicella HPV vaccine, as well as the annual flu vaccine.

"We've been very proactive," said Meredith Kieschnick, medical director of both the Roseland Children's Health Center and the Elsie Allen Health Center.

"We don't just want to vaccinate kids, we want them to come in for their &‘well teen exam' and get some health promotion around all their vaccines," she said.

Kieschnick, the lead pediatrician for Santa Rosa Community Health Centers, which operates the two clinics, said that half the patients at Roseland Children's Health Center, about 1,300 kids, will be affected by a new law that requires all students entering grades seven to 12 to be vaccinated with the Tdap booster for pertussis, or whooping cough.

Of these young patients, 89 percent already have received the Tdap vaccine, she said. Elsewhere in Sonoma County, immunization rates are far lower.

In 2009, 324 of the 6,109 Sonoma County kindergartners had a "personal-belief exemption" from at least one vaccine. The resulting percentage of exempted kindergartners was 5.3 percent, more than twice the state's overall 2.03 percent.

The percentage of fully immunized students entering kindergarten classes in Sonoma County has steadily declined from 92 percent in 2002 to 88 percent last year, according to state records.

The best way to prevent pertussis among infants, children, teens and adults is to get vaccinated, according to the federal Centers for Disease Control and Prevention. While pertussis in children and adults can often be mild, it is this group that usually spreads it to infants, who are at high risk of complications.

Six of the nine Sonoma County school districts in which the percentage of fully immunized kindergartners is less than 80percent are in the west county. Two of these districts, Sebastopol Union Elementary and Twin Hills Union Elementary, were at 60 percent, a state Department of Public Health analysis said.

At Sebastopol Independent Charter School, a K-8 school of about 250 students, only five of the 42 children who entered kindergarten in 2009 were up-to-date with their full schedule of vaccines. All 37 students had a personal-belief exemption on file at the school.

Susan Olson, executive director of Sebastopol Independent Charter School, said the full-immunization rate does not fairly reflect the number of students who are "partially immunized" and that some parents tend to choose which vaccines they want for their children.

"Many, for example, do not choose to do the chicken pox vaccine even though it's required," Olson said.

She said she recently received notice from the state about the new Tdap requirement, which would affect 55 students going into the school's seventh and eighth grades in the fall.

"What we'll do is what every other school will do and send notices to our families," she said. "We don't get involved in telling parents what to do with their child."

Olson said her job as an educator "is to ensure that we as a school and as a community are following the law,"

She said that regardless of the number of parents who decided to obtain an exemption, it's going to be a lot of work informing parents and getting immunization records and waivers up to date.

Notifications to parents will be sent out in the spring "so they have time to make an appointment and get it taken care of."

Dr. David Smith, a pediatrician with Annadel Medical Group, said he didn't think the task of vaccinating thousands of preteens and teens would be overwhelming.

"Logistically, it should be easy to do," Smith said, adding that the most recent pertussis outbreak has been in the news for a year and a half.