By using spatial analysis software and medical records to identify clusters of under-immunization and vaccine refusal among Kaiser Permanente members in Northern California, researchers don't just know where anti-vaccine sentiment is more prominent - that correlates to voting registration and has been well-documented - but now they also know how long the anti-vaccine beliefs have been evident.
They reviewed the immunization records of more than 154,000 Kaiser Permanente Northern California members between birth and three years-old. All the children were born between 2000 and 2011 and were covered continuously by Kaiser Permanente, the de facto official insurance/hospital of state government and provides health care for about 40 percent of the insured population in 13 Northern California counties. To identify the clusters of under-immunization and vaccine refusal, they used spatial analysis software to map vaccine to geography.
The Centers for Disease Control's immunization schedule recommends a minimum of 17 separate injections during a child's first two years of life, including for hepatitis A and B, diphtheria, tetanus, pertussis, influenza, polio, measles, mumps, rubella, and pneumococcal virus. They lower risk of vaccine-preventable diseases, while nonmedical immunization exemption and refusal have been associated with increased community risk of measles and pertussis (whooping cough).
The CDC considers children under-immunized when they miss one or more recommended vaccine doses before age three, while vaccine refusal means not allowing a child to receive any vaccines. Under-immunization ranged from 18 percent to 23 percent within clusters, compared with 11 percent outside clusters. Between 2010 and 2012, geographic clusters of under-immunization were found in:
- the East Bay (Richmond to San Leandro);
- Sonoma and Napa counties;
- a small area of east Sacramento (the progressive bastion in Davis);
- northern San Francisco and southern Marin counties; and
- a small area of Vallejo.
"Shot limiting," in which parents limit the number of injections or antigens that children receive during a pediatric visit to two or fewer, was found to cluster in similar areas.
Vaccine refusal ranged from 5.5 percent to 13.5 percent within clusters, compared with 2.6 percent outside clusters. Between 2010 and 2012, geographic clusters of vaccine refusal were found in:
- the East Bay (El Cerrito to Alameda);
- Marin and southwest Sonoma counties;
- northeastern San Francisco;
- northeastern Sacramento County and Roseville; and
- a small area south of Sacramento
The analysis was not designed to figure out why children in some areas are less likely to be fully immunized but the answer is clear; after Andrew Wakefield was published in The Lancet linking vaccines to autism, progressives on the coasts rushed to embrace it, and then celebrities such as Jenny McCarthy and Robert De Niro did also.
The authors note that this study will be useful for targeting outreach efforts in anti-vaccine hotbeds. They are easy to spot.
Citation: Lieu TA, Ray GT, Klein NP, Chung C, Kulldorff M. Geographic clusters in underimmunization and vaccine refusal. Pediatrics. 2015 Feb;135(2):280-9. doi: 10.1542/peds.2014-2715. Epub 2015 Jan 19. PMID: 25601971.
