Measles Outbreaks Are Concerning, Even to the Vaccinated
Mar 11, 2014

Last week  New York City health officials announced that there was a measles outbreak in Manhattan and the Bronx. So far they have identified 16 cases of measles, representing the worst outbreak in the state in the past 17 years.

After sharing this news with our Vaccinate Your Baby Facebook followers, we began receiving inquiries about measles and the concern of outbreaks.  Below I’ve addressed some of the more common questions, and hopefully they will help people understand why outbreaks are a concern for everyone, even the vaccinated.

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

Measles is certainly unpleasant, but it can also be quite dangerous. As many as one in three people with measles develop complications to include pneumonia, miscarriage, brain inflammation, hospitalization and even death.  Infants under one year of age, people who have a weakened immune system and non-immune pregnant women’s are at highest risk of severe illness and  complications.  One out of 1,000 people with measles will develop inflammation of the brain, and about one out of 1,000 will die.

How contagious is measles?

One of the most challenging things about containing the spread of measles is that it is highly contagious.  The virus resides in the mucus of the nose and throat and once an infected person sneezes or coughs, droplets spray into the air and spread the disease to others.  The most amazing part is that the droplets remain active and contagious on infected surfaces for hours.  Therefore, you could be in the same place that an infected person once was, and still get sick even if you never encounter them face to face.

How effective is the measles vaccine?

Fortunately, the measles vaccine (which is part of the MMR vaccine) is highly effective against the virus, especially after the recommended two doses.  About 95 of every 100 children will develop immunity after one shot (typically administered between 12-15 months), and about 99 of 100 children will develop immunity to measles after two shots (with the second shot recommended between 4-6 years). Immunizing that additional 4 percent of children a second time is important when trying to protect against a disease as highly contagious as measles. However, with the challenges we’ve faced in obtaining global vaccine coverage, we see that measles is still quite common worldwide.  There are an estimated 20 million cases each year and 164,000 deaths.  (For more information on measles in the United States and worldwide, visit the Global Elimination page.)

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

The MMR vaccination timeframe hinges upon the passive protection that children get against measles, mumps, and rubella in the form of antibodies from their mothers. These antibodies can destroy the vaccine virus if they are present when the vaccine is given and therefore can reduce the efficacy of the vaccine.  By 12 months of age, almost all infants have lost this passive protection and no longer have the antibodies that will interfere with the protection offered from the vaccine.  However, this window may differ slightly by child and is often the reason we see children who contract measles before they have a chance to be vaccinated.

How many of the cases in New York were in vaccinated individuals?

Whenever there is an outbreak people often ask how many of cases have occurred in people who had been previously vaccinated.  Although we don’t know all the specifics yet, we do know that out of the New York cases seven are adults, nine are children and four patients have been hospitalized. CBS 2 reports that most of the pediatric cases have been in children too young to be immunized and that two cases have been in patients where their parents refused to have them immunized. In regards to the adults, the vaccination status is often unknown as adults rarely have documentation of measles vaccination that they may have received as a child.  However, this is a good reminder of the importance of adult vaccination.  And since the recommendation of the second dose didn’t come about until the early 1990’s, it’s probably that most adults are unknowingly undervaccinated.

Typically this question gets to the heart of the vaccine efficacy.  If we look at the decade before the measles vaccination program began, we can see just that measles vaccination has been largely effective.  For instance, there was about 3–4 million people in the U.S. infected each year, of which 400–500 died, 48,000 were hospitalized, and another 1,000 developed chronic disability from measles encephalitis. Fortunately, widespread use of measles vaccine has led to over a 99% reduction in measles cases in the United States compared with the pre-vaccine era.  In 2012 there were only 55 cases of measles reported in the United States.

Why should I be concerned about this outbreak?

Even though the risk of disease may be low for a fully vaccinated child or adult, we must consider that there are still people who remain vulnerable. For example, children under a year old who haven’t been vaccinated as explained above, as well as children who haven’t had their second dose who may only remain at greater risk.   And of course there are those, both children and adults, who can’t receive an MMR vaccine due to various medical reasons.  They must rely on protection from those of us who can.

How common are measles outbreaks in the U.S.?

Since measles was declared eliminated in the U.S. in 2000, cases that occur in this country are heavily monitored.  Each year about 60 people in the U.S. are reported to have measles. However, in 2013 we recorded the second highest number of cases in a single year since elimination with 189 cases.  About 28% of these cases came from patients who were infected in other countries and brought it back to the U.S. where they spread it to others. This caused 11 measles outbreaks in various U.S. communities, including the largest U.S. measles outbreak since 1996 (58 cases). (See Measles—United States, January 1-August 24, 2013 for more information.)

According to a recent report in The Examiner, measles is being seen all across the country this year.  For example:

Massachusetts:  The Massachusetts Department of Public Health stated that they’ve seen six measles cases so far in 2014.   Typically they see about six for the entire year, with the exception of 2011 when they had 24 measles cases, and 2006 when there were 19.

Rhode Island:  On March 2, the Rhode Island Department of Health announced that staff and patients at two hospitals and a walk-in clinic may have been exposed to measles in the week prior. An unvaccinated patient was seen at several facilities for an illness that meets the diagnostic criteria for a probable case of measles. Laboratory confirmation is pending.

Pennsylvania:  Back in February, authorities from Pittsburgh were on alert after a vaccinated college student, who had recently traveled to New York City, had contact with a measles patient and fell ill.

Illinois:  In March a county health department was concerned when it was discovered that one of two measles patients had attended a volleyball game between two schools.  The story indicated that there were at least a dozen students from both schools that had religious immunization exemptions, which is not surprising considering that Illinois has over 8,000 students who have religious exemptions to school vaccinations and therefore remain unimmunized.  (See an example of an outbreak based on religious refusal of vaccination here.)

California:  Current outbreaks include two new cases of measles reported in San Diego County last week with one patient who is believed to have contracted the disease during recent travel to the Philippines where there is a measles epidemic.  Orange County has reported five measles cases so far this year, and the local news claims that the most recent case may have exposed others to the illness while at a hospital emergency department.  And in Contra Costa County, a college student who visited the Philippines was diagnosed with measles in mid-February and has spread it to two additional family members.

As the year progresses, we’ll have to wait and see just how 2014 will compare to previous years in regards to measles outbreaks.  In the meantime, the best way for our readers to stay informed would be to follow your local public health department’s alerts and media announcements to ensure you are getting updated on infectious disease outbreaks in your local area.  You can also visit Healthmap to track outbreaks of diseases near you.  

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