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Many states allow parents to opt-out of vaccinating their children due to philosophical (i.e. fear that the vaccine will cause autism, a theory that has been totally disproven) or religious beliefs. These beliefs are called personal belief exemptions, or PBEs. In 2016, the California Senate passed a bill to eliminate PBEs from the state’s school-entry mandates. Passage of that bill left vaccine-hesitant parents with only one legal option to keep their kids from getting vaccinated. That option is called a medical exemption, or ME, which must be obtained from a licensed healthcare provider. Medical reasons that would prevent vaccination include a compromised immune system (from medications like chemotherapy and steroids, or illness that effects the bone marrow), pregnancy, encephalopathy (brain injury) from a previous vaccination, a moderate to severe infection or illness, a personal or family history of seizures (applies to measles, mumps, and rubella (MMR) and varicella vaccines), and an allergic response to a vaccine.

Last year, a study was published that looked at the number of MEs in California after PBEs were outlawed. From 2000 to 2015, the percentage of kindergarteners with MEs remained steady at about 0.17 percent. The percentage of PBEs rose steadily from 0.88 percent in 2000 to nearly three percent in 2015. In 2016, PBEs dropped to 0.5 percent, but MEs rose to 0.5 percent, which is a threefold increase. Overall, the rate of total exemptions went from just over three percent in 2015 to one percent in 2016. When the authors of the study drilled down into the data, they found that the counties with the highest rates of PBEs before the ban, became the counties with the highest rates of MEs after the ban. This suggests that vaccine-hesitant parents may have successfully found practitioners willing to issue MEs. If true, this practice of issuing MEs would be inconsistent with the recommendation from the American Academy of Pediatrics to reserve MEs for children who have real medical contraindications.

Although the number of kindergarteners with any vaccine exemption decreased in 2016, the California law contained a grandfather clause that allowed all students with PBEs who entered kindergarten prior to 2016, to attend school and be unvaccinated up to seventh grade. Combining this with the rise of MEs in 2016, strongly suggests that some portions of California may remain susceptible to outbreaks of vaccine-preventable illness due to dilution of herd immunity, a concept in which a group of people, or herd if you will, become more susceptible to illness as the number of vaccinated herd members decreases. Sadly, it also suggests that a number of my colleagues may be more interested in pleasing the parent’s wishes instead of protecting the health of their patients.

For more information on vaccine contraindications go to:


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