Study: Anti-vaxxers tend to cluster in similar geographic regions

With vaccination rates for children curiously dropping in certain regions – some of it spurred by the anti-vaxxer camp – Kaiser Permanente sought to gain a clearer understanding of why, using data from its EHR in Northern California to discern patterns. In a study with Pediatrics, researchers found geographical clusters, in this instance around San Francisco, […]

With vaccination rates for children curiously dropping in certain regions – some of it spurred by the anti-vaxxer camp – Kaiser Permanente sought to gain a clearer understanding of why, using data from its EHR in Northern California to discern patterns.

In a study with Pediatrics, researchers found geographical clusters, in this instance around San Francisco, where the anti-vaccine sentiment among parents has a strong presence. The goal of the study was to determine the regional clusters and to evaluate whether “vaccine refusal clusters may pose barriers” in achieving better immunization rates, and thus improve public health and reducing outbreaks of whooping cough, the flu and measles, among other illnesses.

The study cuts straight to the often-vexing issue of vaccinations. It provides potentially helpful data and methods for clinicians, researchers said, noting that it’s among the first to use spatial scan statistics, which could be a “useful tool to identify locations that deserve increased public health and clinical attention.”

Often at issue is people who believe vaccines in young children can be more harmful than beneficial and could lead to the onset of autism, ideas that have been debunked by medical experts worldwide. Another factor in under-vaccination could be parents who don’t want their child to receive multiple shots in one visit. The CDC recommends some 17 shots by age 3 for a number of vaccines, including whooping cough, rubella, polio, mumps, hepatitis and others.

The study indicates that under-vaccination and refusal to vaccinate are often linked by region, which could put clinicians in those regions at a disadvantage in achieving national benchmarks and health outcomes.

“Because these rates are used in national quality metrics, some physician groups are at risk for being evaluated as delivering lower-quality care based in part on factors that may arise from the social environment,” the study notes.

In the regions studied, about 18 percent of children weren’t fully vaccinated by age 3, while in surrounding regions the number was pegged at 11 percent, according to the study. The study population was nearly 155,000 children across the broader Bay Area and its exurbs, with the highest resistance in northern counties like Marin, Sonoma, Napa, eastern portions of Sacramento and part of the East Bay.

In addition to looking at the anti-vaccine component, researchers also found that poorer communities had higher rates of not being vaccinated. For instance, the city of Vallejo, in Solano County, had a rate of non-immunization of 23 percent by age 3, although the study notes that all subjects were members of Kaiser insurance, meaning cost was not the barrier.

Flat-out refusal for all vaccinations wasn’t the norm. Instead, under-vaccination was more common. Using ICD-9 codes, researchers found the refusal rate was 3.5 percent. For under-vaccination, the rate “ranged from a low of 9.2 percent in Santa Clare County to 17.9 percent in Marin,” according to the study.