Medical Vaccine Exemptions Increase Following California Elimination of Personal Belief Exemptions

Boy getting vaccine
Boy getting vaccine
Medical exemption can be obtained with a written letter from a licensed physician with an explanation of why vaccination would be unsafe.

Medical exemptions increased 3-fold following the passage of California Senate Bill (SB) 277, which eliminated the personal belief exemption provision from school-entry vaccine mandates beginning in the 2016-2017 school year.

Researchers used data from the California Department of Public Health to assess kindergarten enrollment, vaccination, and exemption data. The change in medical exemption percentage from 2015 to 2016 was calculated for counties, and the correlation between medical exemption percentages in 2016 and personal belief exemptions in 2015 was evaluated by county. 

Medical exemption percentages remained mostly stable between 1996 and 2015. In 2016, medical exemptions increased from 0.17% to 0.51% of enrollments. The personal belief exemption decreased in the same years from 2.37% to 0.56%, indicating an overall decrease in total exemptions from 2.54% to 1.06%.

Within counties, the change between 2015 and 2016 in medical exemption percentages ranged from –1.00% to 3.38%. Previous personal belief exemption rates were positively correlated with the change in medical exemption rates at the county level (n=56; P <.001).

Dr Paul Delamater, lead study investigator, explained that “the increase in medical exemptions means that many regions in the state likely continue to have low vaccination coverage.” He explained that the study also “shows one potential outcome for other states that are considering removing personal, philosophical, or religious exemptions—in this case, that medical exemption tripled the year after the implementation of the law.”


Delamater PL, Leslie TF, Yang YT. Change in medical exemptions from immunization in California after elimination of personal belief exemptions. JAMA. 2017;318(9):863-864.