.Kaiser Permanente study shows Marin is not alone in underimmunization rates

by Molly Oleson

Parents in Marin choosing not to vaccinate their children are not alone. A new Kaiser Permanente study, published recently in the journal Pediatrics, finds that there are several clusters of underimmunization and vaccine refusal among Kaiser Permanente members in Northern California.

“Such clusters,” the study reads, “could pose public health risks and barriers to achieving immunization quality benchmarks.”

Parents can opt out–by exercising a “personal belief exemption”–of the state law that requires that children entering school for the first time be vaccinated for chicken pox, measles, polio, whooping cough, tetanus, mumps, German measles, hepatitis B and haemophilus influenza type B. Statewide, the percentage of kindergarteners claiming personal belief exemption grew from 1.56 percent in 2007-08 to 3.15 percent in 2013-14. And in Marin, although the number jumped back down to 6.45 percent in 2014-15, it nearly doubled from 4.2 percent in 2005 to 7.83 percent in 2012-13.

The study includes analytics of electronic health records among children born between 2000 and 2011 with membership in Kaiser Permanente in Northern California, drawing from a population of more than 154,000 children across 13 counties with continuous membership from birth to 36 months of age.

It identifies five statistically significant clusters of immunization among children who turned 36 months old during 2010-2012. Within clusters, the underimmunization rate ranged from 18 to 23 percent, and the rate outside them was 11 percent. Vaccine refusal also clustered, with rates of 5.5 percent to 13.5 percent within clusters, and 2.6 percent outside of the clusters.

Spacial scan statistics were used to identify these clusters, and the study’s conclusion reads, “Spacial scan statistics may be a useful tool to identify locations with challenges to achieving high immunization rates, which deserve focused intervention.”