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By Bloomberg

More parents are leery about vaccinating their children, even against once-common diseases like measles and whooping cough. New research suggests their beliefs are contagious too.

A groundbreaking study of 154,424 children covered by Kaiser Permanente in Northern California found five geographic clusters where children were significantly more likely to be underimmunized by their third birthday, including almost 1 in 4 toddlers in part of Vallejo, a city in the San Francisco Bay area. The approach may help doctors identify communities where parents are the most concerned and the chance of an outbreak is highest, the researchers said.

The findings published in Pediatrics confirm long-held speculation that opposition to immunizations can concentrate in communities, increasing the risk of outbreaks, said lead author Tracy A. Lieu, a pediatrician and director of the Kaiser Permanente Division of Research. They also bolster earlier findings that the number of children who aren’t getting the recommended vaccines, or receiving them on time, is on the rise.

“While complete refusal of all vaccines is quite rare, we know parental concern about vaccination has increased in the past decade,” she said. “We need to learn a lot more about what are the effective ways of communicating with parents.”

Concerns Debunked

While the poor have long had lower rates of vaccinations because of their costs, the ranks of children who haven’t had their shots have been climbing in other categories because of fears that immunizations may hurt developing bodies and even lead to autism -- concerns that have been debunked in numerous studies.

The findings published in Pediatrics are timely, coming amid an outbreak of measles in children and young adults who visited Disneyland and Disney California Adventure Park last month. Of 28 people who were infected, just three were fully vaccinated, the state’s Department of Public Health said in an e-mail on Jan. 15.

The number of parents who want an alternative vaccine schedule is also growing, as many don’t want their children to receive three, four or even more shots during the same doctor visit. The U.S. Centers for Disease Control and Prevention recommends a raft of immunizations for hepatitis, measles, mumps, rubella, polio, tetanus and other infectious diseases, requiring at least 17 injections by age 3.

California Clusters

Five areas scattered across Northern California yielded the highest rates of undervaccination, including the East Bay, Sonoma and Napa, eastern Sacramento and northern San Francisco to southern Marin County. About 18 percent of children in those areas weren’t fully vaccinated at age 3, compared with 11 percent in nearby regions. In Vallejo, 23 percent of the children weren’t up-to-date on their shots.

The results weren’t consistent across socioeconomic and demographic groups. Partial immunization was seen more often in poor neighborhoods and in those where graduate degrees were most common. Asians, Hispanics and those in families with higher incomes were more likely to be fully immunized. Cost shouldn’t have been a problem in the study since everyone had insurance and Kaiser fully covers vaccinations, Lieu said.

The study was funded by the Patient-Centered Outcomes Research Institute, an agency created by the Patient Protection and Affordable Care Act to improve the quality of evidence used to make health decisions. It is part of the largest study backed by the institute, which is looking at how parents make vaccine decisions for their children so doctors can better respond to parents’ preferences and concerns, Lieu said.

Electronic Records

The research is one of the first forays into digital epidemiology, enabling researchers to use electronic medical records and manipulate massive databases to identify emerging public health problems, Lieu said.

“The idea is that by identifying these clusters earlier we can get ahead of them,” she said. “Maybe we can help the clinician be better prepared to talk to parents who have questions about vaccine safety and therefore be able to prevent an epidemic. It can also help them monitor more closely for diseases that we know occur in unvaccinated children.”