Why Should Vaccinated Individuals Worry About Measles Outbreaks?
May 22, 2017

The United States is well on our way to a record year for measles cases.  So far in 2017, we’re on track to see more cases this year than last year.

In the state of Minnesota alone, where a Somali-American community was encouraged to refuse MMR vaccine during visits from Andrew Wakefield and other vaccine critics, a drop in vaccination rates has resulted in a dangerous measles outbreak.  So far, the Minnesota Department of Health has identified 66 total cases spread among four counties, with many cases involving the hospitalization of children.

As the number of measles cases in MN is expected to climb, health departments across the U.S. are beginning to identify other measles cases as well.

For instance, the Maryland Department of Health is investigating a potential outbreak after a patients was admitted to Children’s National Medical Center in the District.  The patient had previously sought medical treatment at Prince George’s Hospital Center in MD, exposing countless people in that area as well.  Meanwhile, a teenaged tourist staying in a NJ hotel contracted measles, and now the New Jersey State Health Department fear other people may have been exposed before the patient was treated at The Valley Hospital in Ridgewood, NJ.

With measles cases emerging across the U.S., and large-scale outbreaks of measles being reported by the World Health Organization in places like Romania and Italy, it’s important to ask if measles outbreaks should be a concern to those who are vaccinated.  

Aren’t vaccinated individuals protected during outbreaks?  And if so, why should we care if others remain unvaccinated?

When it comes to infectious diseases like measles, one person’s decision not to vaccinate can negatively impact the health of others.  There are plenty of unvaccinated individuals who rely on protection from the vaccinated, including children under one year of age who are too young to be vaccinated for measles, individuals who have medical reasons that restrict them from being vaccinated, or people with compromised immune systems.  These individuals are all at great risk of contracting measles and suffering serious complications and the only protection they have comes from those who are vaccinated.

In fact, in order to keep measles from spreading, about 92-95% of the population needs to be immune to the disease.  Unfortunately, in the case of measles, even small pockets of un-immunized individuals can threaten the herd immunity threshold.  This is exactly why we are seeing an outbreak in Minnesota.

What’s the big deal?  Is measles even that dangerous?

Measles is not just an unpleasant illness, but it can also be quite dangerous. As many as one in four people who contract measles will be hospitalized, and one out of every 1,000 will develop encephalitis, a dangerous swelling of the brain that can leave a child deaf or intellectually disabled.  Even when children have access to advanced medical care, for every 1,000 children who get measles, one or two will die.

What are the chances of getting infected?

Measles is so contagious that if one person has it, 90% of people who come in contact with that person who are not already immune will also become infected.  Once an infected person sneezes or coughs, the virus that resides in the mucus of the nose and throat is forced into the air, spreading the disease to others and landing on surfaces that can remain contagious for hours.  One can even contract measles from being in the same place that an infected person once was, yet never encounter them face to face.  And since a person is contagious several days before the rash appears, individuals are often spreading the illness long before they realize they’re infected.

Is the measles vaccine effective?

Fortunately, the MMR vaccine (which protects against measles, mumps and rubella) has been proven to be both safe and effective.  The Center for Disease Control and Prevention recommends that children get two doses of MMR vaccine; the first dose at 12-15 months of age, and a second dose at 4-6 years of age.  With two doses of MMR vaccine, studies estimate the vaccine is about 97% effective at preventing measles.

Vaccination in the U.S. has led to an amazing 99% reduction in measles cases compared to the pre-vaccine era.  In the years prior to 1963, when our nation began a widespread measles vaccination program, it’s estimated that about 3 to 4 million people got measles each year, resulting in about 400 to 500 deaths, 48,000 hospitalizations and 1,000 cases of  encephalitis.

If children are vulnerable until they’re vaccinated, why do we wait until their first birthday to begin measles vaccination?

During measles outbreaks, parents of children who are too young to be vaccinated are often conflicted on how best to protect their children.  The MMR vaccine is not recommended until 12 months of age, but there are times when a doctor may recommend that the vaccine be administered early (as explained in the post “Giving MMR Vaccine Early to Protect Children Against Measles“).

However, this a less than ideal solution.  When a child is in the womb, they receive some passive protection from measles from their mother.  While these protective antibodies help protect them before they’re vaccinated, they begin losing this protection over time.  If a child is vaccinated while they still have these protective antibodies, it can interfere with the vaccine virus and reduce the efficacy of the vaccine.  While studies show that most children will no longer have any passive antibodies by 12 months of age, the timing can differ slightly from child to child.  This explains why some children can contract measles before they are vaccinated.  It also explains why a child who is vaccinated under 12 months of age (due to outbreaks or travel), should receive another dose of MMR vaccine at the recommended age to ensure the best protection available.

Why do some vaccinated individuals get measles?  Doesn’t that prove that the vaccine is not effective?

When an outbreak hits, large numbers of people are exposed to measles, so there are typically a few cases that occur among the vaccinated.  When you consider that many more vaccinated people get exposed but very, very few fall ill, you can contrast that data with the small percentage of unvaccinated individuals who are exposed and the overwhelming majority of unvaccinated individuals who fall ill.  So, while two doses of measles vaccine can be 97% effective, that leaves approximately 3% of vaccinated individuals who may remain vulnerable to infection.  It does not render the vaccine uneffective, but does point out the limiations of all vaccines (since no vaccine is 100% effective) and the importance of herd immunity.

Under-vaccinated individuals are also more apt to fall ill.  This accounts for individuals who may have only received one dose of vaccine versus the two doses that are recommended.  Since a second dose wasn’t recommended until the early 1990’s, there are some adults who may have only had one MMR vaccine and never realized they should get another.

Why should I be concerned about these most recent outbreaks?

Even though the risk of disease may be low for a fully vaccinated child or adult, the risk still exists because we can’t predict which individuals did not fully respond to the vaccine.  Additionally, we must acknowledge the risk that exists among people who can’t be immunized or who are not yet fully immunized.  These people rely on the protection they receive from the larger immunized community.

Containing outbreaks of infectious disease is not only time-consuming, it’s also costly.  In Minnesota, while public health officials have already spent close to a million dollars to track down recent measles cases and contain the outbreak occuring there, we expect the costs to soar even higher.  At a time when our country is bracing for large cuts in public health funding, our best defense is a strong offense, and that can be achieved through prevention and immunization.

Please make sure that you and your family members have received two doses of MMR vaccine.  We must all do our part to put a stop to measles.  

To learn more about the recent measles outbreaks from the medical experts on the front lines of the Minnesota outbreak, listen to a recording of a recent conference call that was held with concerned parents here.  This recording is only available for a limited time, so check it out today.

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