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Policies in California improve vaccine uptake among kindergarteners

Cassandra Pingali

Three interventions in California — two legislative and one educational — appear to have been successful in reducing the rate of undervaccinated children entering kindergarten, according to researchers.

According to Cassandra Pingali, MPH, MS, an Oak Ridge Institute for Science and Education fellow currently working at the CDC’s Immunization Services Division, California experienced a very large measles outbreak in 2014 in which most of the infected children were unvaccinated.

“In order to prevent future outbreaks, California wanted to improve their declining childhood vaccine coverage,” she told Infectious Diseases in Children.

The same year, legislation was passed that required parents to consult with a health care provider before obtaining a nonmedical vaccine exemption for their child. This was followed in 2015 by a campaign to educate school staff on the proper application of conditional admission criteria, which give children additional time to catch up on vaccinations. The following year, California banned all nonmedical vaccine exemptions.

“We felt it was important to take a systematic look at these interventions and examine if public health initiatives such as these are working to improve vaccination rates,” Pingali said.

The researchers used school-entry data collected between 2000 and 2017 to identify the number of children attending schools in the state who did not receive necessary immunizations.

During the study period, 9,323,315 children began kindergarten, and 721,593 were not fully immunized. The researchers found that before any interventions were implemented, the rate of children who had not received all necessary vaccines increased from 7.8% in 2000 to 9.84% in 2013. This rate decreased to 4.87% in 2017, after the three interventions were in place.

The likelihood of kindergarteners having contact with other kindergarteners who were not up to date with their immunizations also decreased substantially during the study period (26.02% to 4.56% [95% CI, 4.21%-4.99%]), they said.

The researchers also looked for geographic clusters of schools with higher rates of underimmunized kindergarteners. They found 93 of these clusters, which included 2,290 schools. Although the number of geographic clusters slightly increased (n = 110) by the end of the study period, the clusters included fewer schools (n = 1,613; 95% CI, 1,565-1,691).

Pingali said California was the first state in over 30 years to ban personal belief exemptions, but other states, including New York, Maine and Washington, have recently passed legislation limiting access to nonmedical vaccine exemptions.

“This will be a great opportunity to compare the effects of similar vaccine legislation across states,” Pingali said. – by Katherine Bortz

Disclosures: Pingali reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.