The Disneyland Outbreak: An Analysis of California’s Vaccination Laws and Subsequent Legislation

The week between Christmas and New Year’s is one of the most profitable times for theme parks, averaging about 24 million people each year (1). The parks swell with numbers as many families visit on vacation, often times with small children. Theme parks like Disneyland in California are famous for being every child’s dream – yet this past holiday, the park was nothing short of a nightmare. Instead of spending time with family, many children ended up in the hospital, diagnosed with the once-U.S.-eradicated measles. 

The outbreak itself was not like most; rather than being unpredictable and hard to prevent, the Disneyland measles outbreak could have been entirely avoided, if more children had been vaccinated. Yet it was the rise in the anti-vaccine movement, catalyzed by Andrew Wakefield’s 1998 paper claiming a link between autism and vaccination, which led to a massive decrease in vaccination rates. The Wakefield paper largely contributed to an increase in personal or religious belief exemptions as methods around the law that mandates vaccination for school children. Based on spatial analyses conducted of these belief exemptions in conjunction with the clusters of intentionally unvaccinated children, California was at a high risk for an outbreak. Furthermore, despite this evidence, no new prevention measures were put in place. It was only after the outbreak that California implemented legislation to mandate vaccination except for people who were medically exempt, destroying the philosophical and religious belief-loopholes in an effort to increase vaccination rates. This is likely due to the fact that such controversial legislation required traction for the fight against the anti-vaccine movement in the efforts to improve public health, and that is what the outbreak became: the necessary, albeit tragic, catalyst that gave California the chance to create stricter laws that advocate for vaccination.

The documented Disneyland outbreak began on January 5th, with an 11-year-old who was unvaccinated and presented with a fever and a rash since the 28th of December (1). As measles is highly contagious, its spread in a clustered, over-crowded theme park was rapid and nearly impossible to contain. Though the index case of the outbreak has not yet been found, the subsequent victims had all been in Disney from December 17th to 20th, with a total of 125 measles cases reported by February 11th (1). Among the 110 who were from California, 28 were intentionally unvaccinated due to personal beliefs (1).  The rise in such exemptions over the past decade can be further understood by taking a closer look at the infamous 1998 paper by Andrew Wakefield.

The paper, originally published in the respected journal The Lancet, described a 12-person study in which Wakefield examined gastrointestinal and neurological problems after vaccination. Following examination of the participants, he made a loose argument that the onset of autism had a link to MMR vaccination (2). Autism, a devastating disease for both the victim and their family, is characterized by difficulties in social interactions and communication. Autism typically presents in toddlers aged one to two years old and often changes the child from playful and social into distant and quiet (3). As one can imagine, the transition from a healthy child to an autistic child is torture for the parents, and often leads to self-blame. The link between autism and the MMR vaccine proposed by Wakefield’s paper provided a preventable, though not proven, reason for the onset of the mysterious disease. Though the root cause of autism is still not definitively known, at the time of Wakefield’s paper it was an absolute mystery; thus, the immediate reception by the public was one of intrigue, rather than dismissal. Since both vaccination and the onset of symptoms of autism occur in the first few years of life, the link between the two became dangerously easy to make (3).

Since its 1998 publication, Wakefield’s paper has since been discredited by many scientists who found no such link between autism and vaccination. However, the causal association stuck in the minds of many. Unlike vaccines, which do nothing visual when they work, the effects of autism are much easier to see. The personal anecdotes of children like Jenny McCarthy’s are far more emotionally appealing than the statistical data against Wakefield (3). As Hilleman said, “Public perception is not often informed by science.” In this case, the public perception was informed by press conferences and nightmare stories about children changing after receiving the MMR (3). By refusing to vaccinate, followers of the anti-vaccine movement began to diminish the herd immunity – the percentage of the population that must be vaccinated in order to prevent an outbreak – and this decrease would lead to significant consequences.

The rise in the anti-vaccine movement came with an increase in personal or philosophical belief exemptions from vaccinations, or PBEs. PBEs occur when a parent has some kind of moral problem with vaccinating their child. Unlike religious vaccine exemptions, which are meant for people whose faith does not allow for ‘invasive medical procedures’ like vaccines, PBEs are typically associated with fears of autism, or fears of vaccine side effects (4). For a person to be granted a PBE they must object to all vaccines, not just one (4). Though this seems radical, the mandate acts as a deterrent. If the exemption mandates that a person cannot be exempt from one vaccine without not getting them all, chances are that most people would prefer to be vaccinated. However, this deterrent is backfiring; with PBEs on the rise, herd immunity is diminishing not for just measles, but for any vaccine-preventable disease.

Prior to the outbreak in Disneyland, 17 states allowed for PBE’s, including California (4). In an article by the Washington Post, author Christopher Ingraham described the “anti-vaccine epidemic” of the state: “Between 2000 and 2013, the percentage of kindergartners in the state with personal belief exemptions to vaccination quadrupled – from 0.77 percent to 3.15 percent. At some private schools, this is as high as 75 percent” (5). With 75% of a private school unvaccinated, areas in the state were running a high risk of an outbreak. Areas with as low as 25% herd immunity, or immunity clusters, make it easy for contagious diseases to spread.

In a paper published by Pediatrics, authors Margeret Carrel and Patrick Bitterman examined the rise in PBEs spatially and in correlation to other trends in California, as well as in overlap with any personal medical exemptions (PBMs). In the study, which was conducted using PBEs and PBMs from kindergarten classes from the years 2001/2002 in comparison with those of 2014/2015, they determined that schools with high PBE rates were clustered separately from those with low PBE rates (6). Additionally, they found that in schools where there were higher rates of PBEs there were also higher rates of PBMs, leading to an overall decrease in the herd immunity of these schools and a significantly more susceptible immuno-compromised population (6). This may be due to the school children from one school having the same doctors. The doctors who are more lenient with exemptions thus create a recipe for disaster: more exemptions in the same school leads to a diminished herd immunity overall. This may seem inconsequential, with many schools in California having a normal herd immunity for measles, but as another study published by BMC Public Health shows, an increase in clusters of unvaccinated people diminishes the overall herd immunity of a society and increases the risk for an outbreak (7).  

Interestingly, both the Carrel and Liu papers were published online after the outbreak occurred, despite the Liu paper being received by BMC Public Health in November 2014 (6). This suggests that perhaps the papers were only published once the public had an eye on California’s vaccination rates, even though the evidence that the outbreak was inevitable was documented at least a month before. The Carrel paper used data on PBEs and PBMs from before the outbreak as well. Thus, the outbreak truly was preventable, and had the information been in the lens of the public sphere, there is a good chance it would have been prevented.

It is likely that the reason why California only implemented the legislation following the outbreak is that it would have had too many opponents and not enough evidence prior to it. To strip people of the right to choose if they are vaccinated or not can be seen as an infringement on individual rights, especially in the case of religious exemptions (8). Additionally, other states that changed vaccination laws recently made more gradual changes; California was implementing a legislation to eliminate all exemptions besides medical, after years of having both. Thus, without evidence of the damage caused by the anti-vaccine movement, California was stuck.

The traction California had for the legislation came after the outbreak, strengthened by the media crisis it created. Articles on U.S. News and CNN titled “Not The Happiest Place on Earth,” and sub-headers “Happiness isn’t the only contagious thing at Disneyland in California” describe the kind of shock people had at the outbreak occurring there (5, 9). A place meant for children and family-friendly fun had become, in all intents and purposes, a crime scene, instigated by the anti-vaccine movement. Alex Berezow of USA Today argued that parents who choose not to vaccinate their kids should be placed in jail; Forbes magazine that “we have yet to develop a vaccine against simple human venality” (5,10). It became a media circus; every day since January 5th a new number of measles cases was recorded; every day another news channel crying out in disbelief over the outbreak. Yet in hindsight, the outbreak was not shocking at all; with all the evidence that predicted it, it should not have been surprising to anyone. Nevertheless, what people are informed about is usually limited by what is presented by the media, and the media is often more effective than scientific fact, especially when pictures of small children with measles and Disneyland T-shirts are broadcasted to the public.

The actual legislation California passed mandates that all vaccine exemptions for personal and religious beliefs are no longer allowed. Beginning in the school year 2016-2017, any children who are unvaccinated but do not have a medical exemption will be forced to be homeschooled, and those who are currently in school have until either entrance into kindergarten or 7th grade (individual checkpoints) to be vaccinated (8). The law applies to public and private schools as well as day care facilities. The legislation makes California the third and biggest state to mandate vaccination to all but those who are medically exempt, with the other states being West Virginia and Mississippi (8). Among the remaining 47 states, 16 still allow for moral exemptions as well as religious and medical (4).

The legislation itself is thus controversial: banning children from public education to be homeschooled has been a center of the argument, as many families cannot homeschool their children. Parents who want vaccine exemptions argue that the legislation “violates California’s constitutional provision guaranteeing the right to a free and appropriate education” (8). Other arguments against the legislation include those based on the Free Exercise Clause, a clause that forbids laws that “seek to restrict acts of faith,” an argument against the removal of religious exemptions (8). However, in response to these arguments is the ruling found in Prince vs. Massachusetts, when the Supreme Court ruled that the First Amendment “does not include parents’ right to expose a child or community to communicable disease or other harms,” and the ever-famous Jacobson vs. Massachusetts, which ruled that the state has the authority to mandate vaccinations to protect citizens against a dangerous epidemic (8). Not only does refusing to vaccinate a child put other unvaccinated children at risk, but the measles virus has now become an epidemic in the U.S. As a proponent of laws that mandate vaccination, California has made a clear and definitive stance against the anti-vaccine movement, with the traction provided by the outbreak.

With the California legislation comes hope for a change in vaccination laws at a federal level. Only three states currently mandate that medical exemptions are the only exemptions allowed for vaccines, leaving 47 other states with possible religious exemptions, and 16 of those 47 with exemptions based on personal beliefs. However, California’s population density gives it significant influence in this country, and the outbreak at Disneyland had worldwide media exposure. Though it is not clear if or when other states will follow suit, the images of children coming down with one of the most vaccine-preventable diseases at Disneyland are unforgettable. In a roundabout way, the Disneyland outbreak was what California needed to push through necessary and logical vaccination law reform, and in the coming years, it is hopeful that the country as a whole will take the necessary steps to prevent another entirely preventable outbreak from occurring.



1.     Zipprich, J. Winter K., Hacker J., Xia D., Watt J., Harriman K; Centers for Disease Control and Prevention. Measles Outbreak – California December 2014-February 2015. MMRW Morb Mortal Wkly Rep. 2015: 64(6):153-154

2.     Wakefield, Andrew. "RETRACTED: Ileal-lymphoid-nodular Hyperplasia, Non-specific Colitis, and Pervasive Developmental Disorder in Children." RETRACTED: Wakefield, Murch, Anthony Et Al, The Lancet, February 28 1998. The Lancet, 28 Feb. 1998. Web.

3.     Offit, Paul A. Vaccinated. New York: Harper Collins, 2007. Print..

4.     "Vaccine Law Information - NVIC." National Vaccine Information Center (NVIC). NVIC, n.d. Web.

5.     Brody, Rachel. "Views You Can Use: Not the Happiest Place on Earth." Us News, 29 Jan. 2015. Web.

6.     Carrel, Margeret. "Personal Belief Exemptions to Vaccination in California: A Spatial Analysis." Pediatrics 136.1 (2015): n. pag. Pediatrics, 1 June 2015. Web.

7.     Liu, Fengchen, Wayne Enanoria, and Traivs Porco. "The Role of Vaccination Coverage, Individual Behaviors, and the Public Health Response in the Control of Measles Epidemics: An Agent-based Simulation for California." BMC Public Health 15.447 (2015): n. pag. BMC Public Health, 01 May 2015. Web.

8.     Yang, Tony Y. "Measles Outbreak as a Catalyst for Stricter Vaccine Exemption Legislation." Journal of American Medical Association. JAMA, 29 Sept. 2015. Web.

9.     Ellis, Ralph. "Measles Outbreak Linked to Disneyland Grows -" CNN. Cable News Network, 23 Jan. 2015. Web.

10.  Willingham, Emily. "The Price of the Autism-Measles Panic, 15 Years Later." Forbes. Forbes Magazine, 21 July 2013. Web.

11.  "Community Immunity ("Herd Immunity")." Community Immunity ("Herd Immunity"). N.p., 16 Apr. 2015. Web.