Disneyland, Measles, and Herd Immunity

When the herd fails to protect the individual

Doctor administers measles vaccine to baby
Joe Raedle/Getty Images News/Getty Images

In January 2015, dozens of Disneyland visitors from across the country left with more than just a picture with Mickey and memories of fireworks and Space Mountain ... they left infected with measles.  The scale of this outbreak probably came as no surprise to epidemiologists and public-health officials who have tracked more cases of measles in 2014 than the past 20 years.  More specifically, according to the CDC, in 2014, there were 23 measles outbreaks which infected 644 people spread across 27 states.

  And to think, in 2000, we Americans declared a "win" on measles in the United States with the perceived threat of indigenous spread quashed. 

Measles is a particularly infectious and communicable disease--much more contagious than Ebola, another disease that has captured the public's imagination in recent months.  On average, a person with measles will go on to infect a whopping 12 to 18 people.   The recent uptick in documented cases of measles is directly attributable to fewer people receiving vaccination for the disease, a decision that puts not only the individual at risk but also the population at large.  Moreover, because measles is so darn catchy, we can't depend on others receiving vaccination to protect us, a phenomenon commonly referred to as herd immunity.

What is measles?

Measles is a viral (paramyxoviral) infection which causes acute systemic or body-wide symptoms.  People with measles first experience a very high fever, and this fever persists through the development of a rash at about one week's time.

  This rash is accompanied by the appearance of Koplik spots, small reddish-white spots on the buccal mucosa (inside of the mouth) which are pathognomonic or specific to the disease.

Here are other acute symptoms of measles:

  • malaise
  • stuffy nose
  • sneezing
  • sore throat
  • cough
  • conjunctivitis
  • yellowish tonsillar exudate or discharge
  • generalized lymphadenopathy or enlarged lymph nodes

People with measles can experience symptoms of the disease for up to 2 weeks.  More rarely, measles is deadly especially in children; in the United States, measles kills about 3 in 1000 people.

In some, measles enters the central nervous system and causes encephalitis or infection of the brain.  Measles can also leave a person susceptible to secondary infections with bacteria with otitis media (middle ear infection), pneumonia and cervical adenitis (inflammation of the cervical lymph nodes) affecting 15 percent of those infected.  Among these complications, encephalitis and pneumonia are most deadly.  (In developing countries, where measles is a scourge, the virus kills untold scores on account of diarrhea which drains malnourished kids of bodily fluids and life.)

Following the onset of rash, people with measles are typically isolated for a week.  Much like Ebola, when a case of measles presents, the government steps in at great expense to the taxpayer.

  Government officials do their best to track down potential contacts.  This practice can be particularly cost and labor intensive especially in the case of air travel (much measles is imported from other countries like the Philippines and India).  An Arizona outbreak at two hospitals ended up costing $800,000. 

Treatment for measles is supportive or symptomatic and includes fluids and antipyretic medications like Tylenol which take aim at fever.  Interestingly, vitamin A can also be given.  Vitamin A apparently proffers some respiratory and gastrointestinal benefit in children although high doses may interfere with antibiotic efficacy; antibiotics are given to treat the secondary infection.  In some cases (pneumonitis), the antiviral drug ribavirin can also be given.

The value of the MMR vaccine

With respect to measles and other infections for which a vaccine exists, the best defense is a good offense.  In the United States, infants are first given the live measles, mumps and rubella (MMR) vaccine between 12 to 15 months and the second dose between 4 and 6 years of age.   At 6 months of age, infants born to measles-immune mothers lose maternal antibodies.  In other words, at 6 months, babies become completely vulnerable to the disease.  Because the measles vaccine is 2.4 times less effective when given prior to 15 months of age, these little ones typically don't receive vaccine unless exposed during an outbreak.

During an outbreak, when unvaccinated people are exposed to measles, they are typically vaccinated for measles and given an intramuscular shot of immune globulin.  If given within 5 days of exposure, the measles vaccine can prevent disease.  Three months after receiving this first dose such vaccinated people must receive a second dose.  Pregnant women and immunocompromised people (think AIDS) shouldn't receive the vaccine. 

Please note that the measles vaccine is very safe; severe allergic reactions are very rare.

Herd immunity

When a sufficient number of people have been immunized for disease, herd or community immunity can kick in.  As long as the rest of us are immunized, unvaccinated members of the community or "herd" are safe.  In order to confer herd immunity, the vaccine must be live and prevent not only the development of the disease in the individual but also the transmission of the disease to others.

As we've learned the hard way, herd immunity with respect to measles is particularly elusive.  In order to make the community safe for those unvaccinated, it's estimated that between 92 and 94 percent of people must be vaccinated for measles.  However, outbreaks have occurred in communities where even more than 94 percent of its members have been vaccinated!

Keep in mind that in some parts of the United States, measles vaccination is far fewer than 92 to 94 percent.  For example, in the US Virgin Islands, only 63.7 percent of the population is immunized.  Stateside, in Washington and West Virginia, only 84.6 percent of the population is vaccinated.  These low vaccination rates leave pockets of people particularly susceptible to measles.

If you or a loved one have yet to receive the MMR vaccine, you need to receive it.  Forgoing vaccination for you or your child is not only a personally irresponsible decision but a socially irresponsible one, too.  Even if you survive the disease, the year-old baby who you infect in the queue at Disneyland, Walley World (big up to my Chevy Chase peeps!) or wherever else might not be so lucky.

In addition to being a medical journalist, I'm also a journalism thought leader and author of what is fast becoming the go-to book on article writing: .  (People likely buy the book because it's priced at a mere $15 but keep it because it's sooo good.  Modesty what?!) In my book, I cite the press given to the antivaccination movement as a classic example of false equivalency: In order to make headlines juicy, journalists have wrongly recognized and reported on the fringe and conspiracy-coated movements which have no scientific or medical basis. 

More specifically--no matter what your favorite celebrity says--MMR vaccination doesn't cause autism!  Medical researchers and physicians have proven time and again that the vaccinations are safe.  In fact, Andrew Wakefield, the man who came up with this fictitious and erroneous connection, was completely discredited and lost his medical license.  Furthermore, his 1998 research paper suggesting the vaccination-autism link was retracted by The Lancet.

Selected Sources

Levinson W. Viral Vaccines. In: Levinson W. eds. Review of Medical Microbiology and Immunology, 13e. New York, NY: McGraw-Hill; 2014.  Accessed 1/25/2015.

Article titled “Mounting a Good Offense Against Measles” by W. Orenstein and K Seib published in The New England Journal of Medicine on 1/24/2015.  Accessed from PubMed on 1/24/2015.

Shandera WX, Kelly J. Viral & Rickettsial Infections. In: Papadakis MA, McPhee SJ, Rabow MW. eds. Current Medical Diagnosis & Treatment 2015. New York, NY: McGraw-Hill; 2014. Accessed 1/24/2015.

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