The attitude of vaccine-hesitant parents claiming nonmedical exemptions for their children has been associated with recent outbreaks of measles, pertussis, and other serious illnesses across the United States.1

In late 2014, a multi-state measles outbreak originating in a California amusement park was linked to 111cases of measles, half of which were unvaccinated individuals.2 After passing Senate Bill 277 (SB277) in 2015 eliminating nonmedical vaccine exemptions, California saw an increase in the number of fully vaccinated schoolchildren.3 In addition, since the passing of SB277, the number of medical exemption claims has also increased 250%, from 0.2% in 2015 to 2016 to 0.7% in 2017 to 2018.3

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These numbers suggest that vaccine-hesitant parents are seeking other avenues to avoid vaccination. From August to September 2017, investigators from the University of Pennsylvania in Philadelphia interviewed health officers in California to assess key themes associated with the recent increase in medical exemptions from vaccination. Published in Pediatrics, the interview results suggest that California’s increasing medical exemption rates could curb the long-term efficacy of SB277.4  

Investigators conducted 34 semi-structured telephone interviews with 40 health officers and immunization staff from 35 of 61 local health jurisdictions in California to parse out the circumstances surrounding increases in medical exemptions. Audio recordings and transcripts were generated from each interview, and investigators independently reviewed and coded transcripts. Characteristics of the interviewees and their local health jurisdictions were also recorded, including average personal belief exemption rates before SB277 and median household income.

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Investigators identified 4 primary themes during coding: (1) the role of stakeholders, (2) reviewing medical exemptions received by schools, (3) medical exemptions perceived as problematic, and (4) frustrations and/or concerns regarding medical exemptions. Study participants typically underscored the responsibility of physicians to stem the increase in medical exemptions. Physicians are responsible for writing medical exemptions, and although health officers typically agreed that the “local health department has no authority to question the…validity of the medical exemptions,” many suggested that the California Medical Board assume a more active role in exemption monitoring. Specifically, interviewees asked that the Medical Board discipline physicians who were implicated in writing “problematic [medical exemptions].”

Medical exemption review and identification of problematic medical exemptions were also highlighted as key intervention points. Many jurisdictions reported such tactics as using a state database to confirm that the signing physicians were licensed, or reaching out to physicians who issued the exemptions and reporting physicians issuing them to the California Medical Board. Just 5 jurisdictions reported tracking all medical exemptions filed by schools, and one of these jurisdictions was mentioned in a civil lawsuit against SB277 filed by a group of parents. Although the lawsuit was later withdrawn, other jurisdictions cited such legal actions as a concern in tracking medical exemptions.

Regarding problematic medical exemptions, most participants indicated that they did not have the scientific authority to invalidate certain claims. However, many did express concern over the “broad range of…contraindications [for] immunization” permitted by California law, which likely contributes to the large increase in medical exemptions following SB277. In addition, since the implementation of SB277, a number of physicians have begun advertising that they will provide medical exemptions for a fee, and unauthorized providers or providers who do not typically treat children — including nurse practitioners, physicians at medical marijuana dispensaries, and dermatologists — have reportedly signed exemptions.

Interviewees typically expressed “frustrations and concerns” during the interview, highlighting the contentious nature of the statewide issue. Specifically, participants expressed frustration with the lack of authority given to local health departments to monitor exemptions and concern about physicians writing problematic exemptions. Many also felt that the burden of implementing SB277 was disproportionately ascribed to school staff. There was consensus among participants that medical exemptions may be serving as a substitute for personal belief exemptions for many vaccine-hesitant-parents. Although the percentage of individuals claiming medical exemptions is low (0.7%), the increase from 0.2% prior to SB277 suggests a worrying trend to many health officials.

Despite the fact that the long-term impact of SB277 has yet to be assessed, information collected just 2 years after its implementation suggests that without legal changes the number of problematic medical exemptions may increase. In general, public health officials suggested a standardized review of medical exemptions by the California Medical Board and increased authority for local health officials. As noted by interviewees and investigators alike, California has made important strides to preserve herd immunity, but there is work to be done in protecting the core objective of SB277.


  1. Phadke VK, Bednarczyk RA, Salmon DA, Omer SB. Association between vaccine refusal and vaccine-preventable diseases in the United States. JAMA. 2016;315(11):1149-1158.
  2. Zipprich J, Winter K, Hacker J, Xia D, Watt J, Harriman K; Centers for Disease Control and Prevention (CDC). Measles outbreak–California, December 2014-February 2015. MMWR Morb Mortal Wkly Rep. 2015;64(6):153-154.
  3. California Department of Public Health, Immunization Branch. 2017-2018 kindergarten immunization assessment – executive summary. Accessed November 12, 2018.
  4. Mohanty S, Buttenheim AM, Joyce CM, et al. Experiences with medical exemptions after a change in vaccine exemption policy in California [published online November 1, 2018]. Pediatrics. doi:10.1542/peds.2018-1051