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Why Did Mumps Spread Through Orthodox Jewish Communities in 2009-2010?

New research published in the New England Journal of Medicine explains why mumps still exists, even with a 99% effective vaccine.

-- by Elijah Wolfson

The Gist

Mumps sound like a health concern for previous generations—something you read about in Victorian novels or see in period films. But, as a new study published today in the New England Journal of Medicine highlights, the infection has not been completely eradicated from U.S. communities.

From June 2009 to June 2010, the Orthodox Jewish communities of Greater New York were shocked to discover a mumps outbreak spreading amongst their teenage children. 

During that year, a total of 3,502 cases of mumps were reported in two New York counties and one New Jersey county. Strangely, 97 percent of mumps patients were Orthodox Jews. In addition, males made up 78 percent of these cases—much more than one would normally expect. 

Stranger still, almost all of these patients had been vaccinated for mumps. The mumps vaccine is extremely effective—in fact, by 2005, vaccination had reduced mumps outbreaks by 99 percent. 

The study authors sought to discover what could cause these statistical anomalies.

The skewed demographics led researchers to the yeshiva—a religious school where Orthodox Jewish teenage men study religious texts. After examining practices in the yeshiva, the researchers determined that the students’ “style of study may have allowed for a particularly efficient transmission of mumps virus.” 

The Expert Take 

According to Amesh Adalja, MD, FACP, an infectious diseases specialist at the University of Pittsburgh Medical Center, "with the close contact that occurred to produce this outbreak, the immunity was likely overwhelmed by the virus."

Yeshiva students often study for long periods of time, using lots of close, face-to-face contact. Referencing many previous studies, the researchers postulate that the risk of infection with mumps may override the protective value of the vaccine in cases where the exposure dose of the virus is large or intensely transmitted. In other words, the yeshiva students may have been unknowingly sending virus-laden saliva back and forth during their all-day study sessions. 

Even though the yeshiva students may have had contact with others in their neighborhoods, mumps stayed inside the Orthodox community because, as Adalja says, "the surrounding individuals who did not partake in the specific activities may not have been exposed to as intense a number of mumps viral particles to overwhelm their immunity enough to allow an infection to take hold."

In addition, says Adalja, no vaccine is 100 percent effective to begin with, and "with time the protection afforded by vaccination falls." This study, and others, note that mumps outbreaks almost always occur in teenagers and college students—those who were vaccinated years ago.  

That’s why, according to the study, the virus spread primarily among males (girls don’t attend yeshiva), why it never left the Jewish community (even though Jews interact plenty with non-Jews), and why the vaccine couldn’t stop the spread 

The Takeaway

It is clear from this and other studies that the mumps vaccine has a waning effectiveness. Typically, the vaccine is given as part of the “MMR” vaccine for measles, mumps, and rubella. The first dose is given to children at the age of 12 to 15 months; the second at age 4 to 6 years.

The issue is that, by a child’s teen years, he or she will be more susceptible to the mumps virus, even if he or she received both vaccine doses in the proper time frame. Currently, the CDC does not recommend that at-risk populations get a second vaccination.

This doesn't mean that you shouldn't get vaccinated—a slightly less effective vaccine is still far and away more protective than no vaccine. In addition, this study found that among the Jewish teens who were infected, those who were vaccinated suffered significantly fewer and less severe complications from the disease. "The vaccine-induced immunity was enough to mitigate the worst effects of mumps infection," says Adalja.

Source & Method

The results of this study were published in the November 1st issue of the New England Journal of Medicine.

A case of “mumps” was, for purposes of this study, defined as an “illness characterized by the acute onset of unilateral or bilateral tender, self-limited swelling of the parotid or other salivary glands lasting at least 2 days, without other apparent cause.” Both confirmed and probable cases were included in the study.

The data used in this study was collected by various state departments, and then sent to the Centers for Disease Control and Prevention (CDC). All cases were tested in laboratories. The CDC published this data in a 2010 Morbidity and Mortality Weekly Report.

Other Research

2006 study published in Clinical Infectious Diseases looked at another out-of-the-ordinary mumps outbreak that occurred at a Kansas university. The goal was to find out why some students got sick while others did not, even though more than 95 percent of students at the college had received the mumps vaccine. The study found that those who got sick were more likely than those who didn’t to have gotten the vaccine more than ten years earlier. 

In 2007, researchers published a study looking at a 2004-2005 mumps outbreak in England. Again, the goal was to more fully understand vaccine effectiveness. The study authors found that the vaccine lost its protective ability significantly over the years: in 5 to 6 year olds, the vaccine was 99 percent effective; by the age of 11 or 12, the vaccine effectiveness had dropped to 86 percent.

The journal Human Vaccines & Immunotherapeutics is planning to publish a research paper in their January 2013 edition that looks at environmental factors that may have contributed to the Yeshiva mumps outbreak of 2009-2010. The study looks closely at the Brooklyn Yeshiva where the outbreak occurred, and compares that environment to other Yeshivas in the geographical region.

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Tags: Epidemics , Latest Studies & Research

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