Jan 27 2015

Disneyland Measles Outbreak Hubbub

This is an ongoing story that isn’t over yet. As it has been raging for days now, most people have probably heard that there is a big measles outbreak starting in Disneyland in California. There are now 87 confirmed cases of measles, 50 of which can be directly linked to Disneyland. Of the 42 people so far whose vaccination status is known, 34 were unvaccinated, 3 were partially vaccinated, and 5 were fully vaccinated.

Yes, this is caused by those who are not vaccinated

One thing is absolutely certain from these numbers – this outbreak has largely been caused by those who are not vaccinated. As you can see, most of those affected are unvaccinated. The vaccination rate for MMR is about 90% in the US. This means those who are unvaccinated were about 67 times more likely to be infected with measles in this outbreak than those fully vaccinated.

If vaccination rates were higher, then herd immunity could have stopped or severely limited the spread of the disease. That is the point of herd immunity – if enough people are protected then the virus is less likely to find a vulnerable host and continue the spread. The vaccine is about 97% effective in those fully vaccinated, which is why there were a few vaccinated people who contracted the disease.

This is all basic epidemiology. It’s practically just basic math. Yet the anti-vaccine loons and conspiracy theorists manage to make the same mistakes every time an outbreak like this occurs.

An article on NaturalNews writes:

It is entirely possible that a vaccinated person spread the disease to both vaccinated and unvaccinated people, which in and of itself shows the lack of effectiveness of vaccines.

If the vaccine for measles — in the U.S., this vaccine is the combination measles, mumps and rubella (MMR) injection — really did work as claimed, then all the measles cases identified at Disneyland would have been in unvaccinated people. But they weren’t.

This is completely wrong. It is entirely irrelevant who the first case was. When experts say that the outbreak was caused by those who are unvaccinated they are referring of the ability of the virus to spread. The first case is irrelevant. Also, the author makes the common trope of arguing that any cases among the vaccinated show the vaccine does not work “as claimed.” This is demonstrably false, and officials claim the vaccine is 97% effective, not 100%. Actually the data show the vaccine is working exactly as claimed.

They also try to blame the outbreak again on the vaccine itself. The CDC reports that:

An estimated 600,000 to 900,000 persons received KMV in the United States from 1963 to 1967. KMV sensitizes the recipient to measles virus antigens without providing protection.

That’s right – they are still trying to blame measles outbreaks on the almost 50 year old version of the vaccine that is no longer used, and whose effects have likely worn off in the population or been erased by getting an updated vaccine. There is also no evidence that the current outbreak is atypical measles as would result from the killed measles virus vaccine from the 60’s.

The numbers are very clear. This outbreak would not have occurred at all, or would have been much smaller, were it not for the large numbers of unvaccinated people in the population.

Measles is a serious illness

The next chapter in the denial of the implications of the antivaccine movement is to claim that measles is no big deal. Meanwhile, one in four people affected by the current outbreak have had to be hospitalized. Being admitted to the hospital is a pretty good marker that an illness is a “big deal.”

Orac has posted an excellent take down of this claim here.

This is an old strategy. A couple of years ago an Australian anti-vaccine author wrote a book called Melanie’s Marvelous Measles. Sure, two weeks of being miserable with a high fever and rash, and a 30% complication rate, is really marvelous.

Antivaxxers Unphased

You can’t reason someone out of a position they did not reason themselves into (original author unknown, but recently popularized by Ben Goldacre in his book, Bad Science). This is now a core bit of wisdom among critical thinkers. Motivated reasoning can make strong ideological beliefs immune to factual refutation. In fact, exposure to contradictory information may even strengthen the belief by triggering motivated reasoning.

It is therefore of absolutely zero surprise that the antivaccine movement is unmoved by this recent outbreak. The mechanisms of denial, misinformation, and distortion are too well established.


The one good thing to come out of this recent outbreak (and the many other recent outbreaks that have been occurring) is that the media and the public finally seem to be catching on that the anti-vaccine movement is pernicious. Previously contained infectious illnesses are coming back because pockets of vaccine refusal are eroding herd immunity.

Even on Fox News experts are making it perfectly clear that children should be vaccinated or there will be more outbreaks like this one.

Popular culture is reflecting the backlash. An Onion article completely nails it (like only satire can):

I Don’t Vaccinate My Child Because It’s My Right To Decide What Eliminated Diseases Come Roaring Back

I’ll end with the money quote:

The decision to cause a full-blown, multi-state pandemic of a virus that was effectively eliminated from the national population generations ago is my choice alone, and regardless of your personal convictions, that right should never be taken away from a child’s parent. Never.


31 responses so far

31 thoughts on “Disneyland Measles Outbreak Hubbub”

  1. evhantheinfidel says:

    It is ASTOUNDING that antivaccers can think that a minority of unvaccinated people being the majority of those infected could possibly be supporting evidence for the inefficacy of vaccines.

  2. jesse.huebsch says:

    I think the persistence of anti-vaccine sentiment is due to the social cover it has been given. It is somewhat surprising considering the risk adverse nature of modern parenting, but at least in the past it has been given an implicit pass, if not been considered ‘cool’.
    I still think that the tipping point will be when the average parent in the at risk of not vaccinating demographics has a friend of a friend on Facebook that has a kid with a vaccine preventable disease, especially if they are hospitalized. Being criticised on Facebook probably mostly only strengthens convictions, having your kid being rejected from play dates and birthday parties because they are too risky by not being vaccinated will be the end of the mass anti-vaccine movement.

  3. pdeboer says:

    Hey Steve,

    Is there any worthy discussion to be had about whether the infected are antivax?

    I’d like to see just how many slipped through the cracks and missed the vaccine, how many were fence sitters who didn’t get the vaccine, and how many were antivax.

    Maybe even interview one of the two latter on the show?

  4. John Danley says:

    There remains no dispassionate control group of the mind once we have committed ourselves uncritically to a “controversial” narrative. In many ways, this is just another extension of the political backlash against perceived collective or state control (vaccines = evil socialism).

  5. MJC says:

    Jesse, which do you think is more potent, the perceived risk of vaccination or the genuine risk of reemergence? Vaccinia virus is orders of magnitude less virulent than Variola, but it is certainly not benign and Dryvax would not be likely to pass muster with the FDA these days. While smallpox was endemic the one in a million risk of dying from vaccination was far better than the 30% risk of death from a wild-type smallpox infection but once eradicated the small risk of vaccination could no longer be justified given the effectively null risk of a wild infection. Now that we have nearly eliminated autochthonous transmission of many of these pathogens in the United States people are inclined to ask the same question. However in this case they grossly overestimate the risk of vaccination and under appreciate the risk of reemergence. It is like reasoning, if I have never been hit by a car before then why should I continue to look both ways before crossing the street.

  6. jesse.huebsch says:

    It is not the anti vaccine parents attitudes I am talking about, but everyone else. I think right now (or at least a few years ago) enough people are willing to down rate the risk of the vaccine preventable diseases to allow the pockets of anti-vaccine sentiment to have social license. What I am suggesting is that this general perception of risk will change from “people can do there own thing, it doesn’t really affect my kids” to “non-vaccinating their kids is an unacceptable risk to my kids”. When the anti-vaccine parents start feeling their kids are being excluded from activities and that they are being looked down on as ‘bad’ parents then the pockets of anti-vaccine sentiment will shrink rapidly.
    Think in terms of all the parents who think letting a ten year old walk to school is too risky. How much of a shift in how they perceive measles does there need to be before the same parents ask about vaccines before sending birthday party invites?

  7. BBBlue says:

    “The primary reason why many were choosing not to vaccinate is they perceived a low risk of illness from vaccine-preventable disease.”


  8. Willy says:

    I had measles as a child and am now in my early 60s. Would a vaccination be appropriate for folks like me?

  9. edwardBe says:

    Willy, there are tests for immunity that will tell you your antibody titer. They are available privately online as well as through your doctor. It is a “Measles, Mumps, Rubella Antibody” test.

  10. BillyJoe7 says:


    Measles infection almost always produces life long immunity.
    Do you actually have measles though?

  11. BillyJoe7 says:

    …I meant “Did you actually have measles…”

  12. Adam says:

    Excellent post; a welcome read among all of the anti-vaccine misinformation out there.

    Interesting too how the statistics is bang on what is expected. An unvaccinated individual will be infected when exposed 90% of the time; the similar rate for a vaccinated individual even in this outbreak is at least 50-67X less likely to be infected – 90/67=1.3% primary vaccine failure rate. This lies exactly in the range of 98-99% vaccine effectiveness that studies based on analysis of the immunization status of cohorts of infected individuals in prior outbreaks demonstrate; e.g.:

    It allows a calculation of just how many people were exposed to measles at Disneyland. If 37 unvaccinated cases were 90% of those unvaccinated and exposed, that’s a total of 37/0.9 = 41 unvaccinated people exposed. If 5 people were 1.7% of those vaccinated and exposed, that’s a total of 5/0.017 = 294 vaccinated people exposed. Thus, in the current outbreak originating at Disneyland, a (statistical) total of 294+41 = 335 people were originally exposed – a giant number. Of those, 41 were unvaccinated and 37 became infected (4 were very lucky), while 294 were vaccinated and 5 became infected (289 were immune thanks to the vaccine).

    The fact that a small number of vaccinated people became infected is in no way a surprise (no vaccine is 100% effective), but realizing the true scope of the exposure reveals just how remarkably effective the vaccine is, and how well herd immunity has helped control the outbreak.

    What if, for example, the original 294 exposed and vaccinated individuals at Disneyland had no immunization with measles vaccine at all in addition to the 41 that were exposed and unvaccinated? A 90% infection rate would statistically have led to a total of 37+0.9*294 = 302 measles cases (i.e., 265 cases in the population that was actually vaccinated compared to 6 in reality, plus the original 37 infected unvaccinated individuals) compared to 43 in the current outbreak (as of reporting on 1/22) – so at least 7X more cases. This theoretical outbreak would surely spread out of control (as they did prior to measles vaccination).

    Additionally, how many cases would have been expected if the vaccination rate were, say, 99%, instead of 90%? In this case, 332 of the original 335 exposed people would be vaccinated, leading to 7 cases statistically (i.e., 2% of 332, assuming a 98% vaccine effectiveness). It’s likely all of the remaining 3 unvaccinated and exposed individuals (i.e., 1% of 335 exposed people) would be infected, leading to a total of 10 cases compared to 43 in the current outbreak (as of reporting on 1/22) – so at least 4X fewer thanks to greater herd immunity.

  13. WalterW says:

    Keith Kloor over at Discover makes a pretty convincing case that you cannot assume this measles outbreak is the result of the anti-vax movement; that the media (and skeptics) have fallen into a lazy narrative that overshadows the fact that a much more complicated set of factors may be at work: http://bit.ly/1Czhjvt

  14. mumadadd says:


    Interesting and valid perspective; thanks for the link.

  15. AmateurSkeptic says:

    The Discover article does not assert that recent measles outbreaks (or at least their severity) are not attributable to a lack of vaccinations but rather that not all parents whose children are unvaccinated are strident “anti-vaxers”.

    “A typical measles outbreak will reveal this. There will be children whose parents refused vaccination; children whose parents were unwittingly not up to date for lack of access; affordability or awareness; adults and travellers who didn’t get a needed booster; and babies who are too young to be vaccinated.”

    The principal focus of the article was how to most effectively reduce vaccination non-compliance.

  16. tmac57 says:

    I don’t think that we can discount the effect that strident anti-vaxers might be playing in the mindset of parents who aren’t at all anti-vax. They put their message out there in various levels of discourse that range from “vaccines are poisoning our precious babies!” to “maybe we should slow down the vaccine schedule”.
    Once the message of doubt is out there, even parents who reject the more extreme version of fear mongering, might be left with this niggling uneasy feeling about how necessary or safe some vaccines might be, causing them to delay or skip vaccines.
    They hear all of this talk and controversy, and probably aren’t savvy enough to sort the BS from the science, and are left baffled and uncertain which action to take. And doing nothing could be the easier path.

  17. AmateurSkeptic says:

    Good point, tmac57.

  18. ccbowers says:


    In the US, the recommendation is based upon the year you were born. The cutoff year is 1957, and people born before that are considered immune from measles and mumps, which means that routine vaccination is not recommended for that age group. I’m not sure what the recommendations are for other countries, since they could be different based upon the circumstances in each country several decades ago.

  19. ccbowers says:

    Adam addresses the point that came to my mind when I looked at the numbers, but he approached it from the other side (i.e. he looked at expected infection rates of immunized versus nonimmunized to people exposed to the virus).

    My first thoughts were that any raw numbers that showed how many were immunized (5) versus not (34) would appeared skewed to the lay person, because (despite the antivax movement) the vast majority of children even in CA are vaccinated. Even for MMR in CA, the figure is around 90%, and many states are higher. Assuming that 90% of those exposed to measles in Disney Land were vaccinated, which is a reasonable/conservative figure given that people from all over the US visit, having 5 vaccinated people get the measles is pretty much what you would expect for a vaccine that works as well as MMR does.

    You can run the numbers from many angles, and they all converge on the same idea. The MMR really did protect people as expected. I hope this story is enough of a wake-up call for parents and soon-to-be parents to sway things. For a disease that was all-but-eliminated from the US to come back at all, when there is a highly effective vaccine still widely available, is a shame. Although not as big of a comeback as Pertussis, the reason for the measles comeback is more easily tied to vaccine rates as the primary/only cause.

  20. grabula says:

    @walterW – maybe I misread that article but I didn’t see the case being made that you claim it does. I DO see a case being made for not being so harsh on the outliers – vaccine hesitant parents who are undecided as to what the right choice should be.

    If he is arguing your point and I missed it, then Adam’s post above yours has some pretty convincing data in its links indicating he’s probably wrong.

  21. Willy says:

    ccbowers: Thanks. I’m 1952 and I think I did have measles, but am now wondering after being asked by BillyJoe. Anyone who would know for sure is no longer around. I have always assumed that “everyone” from my time and before got measles, mumps, and chicken pox. I “know” my sister had mumps because of a family picture of her looking like a chipmunk with stuffed cheeks.

  22. Einslaten says:

    If 100 people are exposed, and 10% are not vaccinated, and there is 90% chance of an unvaccinated person catching the disease and a 3% chance of the vaccinated person catching the disease, there should be 2.7 vaccinated people per 100 catching the disease, and 4.5 unvaccinated people per 100 catching the disease. So of the 42 people who caught it from the source, if 32 were unvaccinated, there should be 20 who were vaccinated, so the unvaccinated percentage is likely lower than 90%, at Disneyland.

  23. Willy says:

    BBBlue–That quote comes from an interview shown on CNN Friday PM (AC 360). I mentioned it on the anti-vaccine tropes thread. Thanks for providing the link so I could see my post was indeed accurate. When Wolfson–a freakin’ cardiologist!!!–said “My child is pure”, I almost vomited..

  24. hwastrel says:

    as of yesterday evening, 107 cases (http://www.chicagotribune.com/lifestyles/health/chi-science-parents-vaccinate-kids-measles-20150130-story.html)
    let’s start a petition to get Disney to not let the kids in unless they can prove they’re vaccinated.
    Alternative: people sue Disneyland for risking their children’s health.
    If locally- controlled school boards can’t insist on vaccinating kids, & if state & federal health boards can’t insist on vaccinating kids, then Disneyland must screen the visiting cohort. So must all the other popular family tourist sites in the country & everywhere. Not just obviously vital to keeping their clientele from catching deadly preventable diseases, but also saves them from serious lawsuits.

  25. BBBlue says:


    Not just any kind of cardiologist, but an “integrative” cardiologist who is “…proud to be voted Top Holistic MD 2012 by Natural Awakenings Magazine.” http://wolfsonintegrativecardiology.com/

    That certainly explains a lot.

  26. jsterritt says:

    A NYTimes piece making the rounds [1] has some illustrative gems from non-vaccinating parents. It’s a trite article, but one that makes up for much of the false balance that has flawed reporting on the issue. Yes, there is the inevitable quote from Barbara Loe Fisher. But there are also candid side-by-side statements from pediatricians and non-vaccinating parents that highlight the chasm of authority that exists between the expertise of a professional and the ill-considered judgement of lay parents.

    “Kelly McMenimen of Marin County, Calif., said she decided not to vaccinate her son Tobias, saying she did not want “so many toxins” entering his body.”

    “She considered a tetanus shot after he cut himself on a wire fence but decided against it: “He has such a strong immune system.””

    It goes to show how strongly fear motivates parents. Fear coupled with inaction provides a path of least resistance and the lowest bar to entry. For many, it is easier to be paralyzed by fear that to act in accordance with best information. Ms McMenimen seems to deny even the possibility that her son, Tobias, could be at risk: “he has such a strong immune system.”

    This is magical and wishful thinking. Ms McMenimen is assuming her son’s continued good health based on the mere fact that he isn’t dead. From that, she is extrapolating an almost superhuman ability to combat infection and remain healthy (although she worries, incongruously, about “toxins” in vaccines). She makes healthcare decisions about her son based on the false assumption that he is invulnerable. The current measles outbreak is a dangerous lesson in the consequences of this kind of lazy, magical thinking.
    [1] http://www.nytimes.com/2015/01/31/us/vaccine-critics-turn-defensive-over-measles.html?hp&action=click&pgtype=Homepage&module=first-column-region&region=top-news&WT.nav=top-news&_r=0

  27. BillyJoe7 says:

    From the above link regarding the cardiologist who is a vaccine denier:

    “It’s not my responsibility to inject my child with chemicals in order for [a child like Maggie] to be supposedly healthy”…”As far as I’m concerned, it’s very likely that her leukemia is from vaccinations in the first place”…”I’m not going to sacrifice the well-being of my child. My child is pure”…”It’s not my responsibility to be protecting their chilldren”…I could live with myself easily [if Maggie died]. It’s an unfortunate thing that people die, but people die. I’m not going to put my child at risk to save another child”…”If a child is so vulnerable like that, they shouldn’t be going out into society”

    Medical school has obviously failed this person.

  28. Charcot says:

    I think there is an underestimation here of how distrust of medicine and the pharmaceujtical industry, and lack of scientific knowledge play into this. These people are mostly not just kooks. I am not anti-vax, have all vaccinations and if I had chidren they would be too. However, I was born in 1958 and most of my lifetime have been hearing almost constantly about one “Oops” after another from the above two industries. Some greatly exaggerated and some rather serious. This isn’t to say there haven’t been many advances, but the “oopses” get the biggest, most hysterical play.

    The point is, I think some of the anti-vax sentiment is honestly come by given frequent hysterical outbreaks of the damage that this or that medication does. Now you have an anxious parent with a baby, and the doctor is telling them to take these multiple shots for diseases that this parent has never seen. So the conundrum faced by the parent is – stick my little baby full of drugs every time he goes to the doctor for diseases that don’t exist, at least not much; or don’t stick my baby full of drugs for diseases he has little to no chance of ever encountering. Rightly or wrongly, that’s the parental math.

    I think education, not coercion, needs to stepped it up. That NYT woman with the kid whose immune system was too strong to get tetanus? That’s lack of education. If the education doesn’t turn everyone around, it will turn some and you have done what you can do. When the whole vaccination ball got rolling back post-War, no one said “Oh, people who won’t come in to get vaccinated are just dumb, ignorant nutcases.” They said “If we want to get people to come in, we need a public education program.” Which is what they did, and got pretty good compliance.”

  29. jsterritt says:

    Very good points, Charcot. Mistrust of institutions (industry and government) has been woven in to the fabric of our society. And having free-floating anxiety and concerns about trustworthiness is surely to be answered with education and proper marketing — not name-calling and lambasting (my style). Still, listening to your inner demons instead of bedrock-solid scientific information is choosing fear over science, with the stakes being nothing less than the health and well-being of children. When a parent puts their own fear-based Dunning-Kruger above the expert advice of their pediatrician, it is a mistake. Add to this that anti-vaxxers are stoking and preying upon these fears to advance an agenda that hurts us all and providing parents with the illusion of an alternative to science-based health choices for their children and I think you’ll agree some anger and outrage are called for, too.

  30. Willy says:

    On the good news front, I see our famed integrative cardiologist Wolfson is being investigated by the Arizona Medical Board.

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