Giving kids and teens in a New York community a third dose of the measles, mumps, rubella (MMR) vaccine likely helped halt a mumps outbreak in late 2009 and early 2010, according to a new report from the Centers for Disease Control and Prevention.

U.S. guidelines call for kids to get two doses of the MMR vaccine, one at age 12-15 months and the other at 4-6 years. But as evidence from the Orange County, New York, community shows, mumps can spread in very close quarters even when most young people have received both recommended doses.

The study covers a mumps outbreak in the Orthodox Jewish community, which researchers say began at a religious camp in the Catskill Mountains and was spread by a method of schooling involving close one-on-one contact between study partners, known as chavrusas.

In September through December 2009, close to 400 people became ill in one Orange County village and was concentrated at three local schools.

"Most of these outbreaks of mumps occur in very crowded settings," said Dr. Preeta Kutty, a CDC researcher who worked on the report. "Although the majority of the children (who got mumps) had received two doses of the vaccine, the intensity of exposure overcame that protection."

Because it can take a few days for mumps to cause symptoms, Kutty said infected students may have been exposing their study partners without knowing they were sick.

When other outbreak-control methods such as isolating sick children failed, public health workers stepped in and offered village students in grades 6 through 12 a third dose of the MMR vaccine in January and February 2010.

In their report on that intervention, Kutty and her colleagues found the rate of new mumps attacks in that age group dropped from almost 5 percent of kids in the three weeks before vaccination to 0.13 percent a few weeks after the extra doses were given.

Village-wide, mumps attacks fell from 0.86 percent to 0.21 percent, the research team reported Monday in Pediatrics.

The most common vaccine side effects were redness and swelling from the shot and achy joints and muscles.

Mumps is caused by a contagious virus that causes salivary glands to swell, as well as fever, headache and tiredness. Complications of a mumps infection include inflammation in the brain, testicles or ovaries.

Kutty said even among people in the New York village who didn't get a booster dose of the MMR vaccine, so-called herd immunity likely kept them protected. Out of 2,178 students who had already received two doses of the vaccine, more than 80 percent chose to receive a third during the outbreak.

Still, the researchers can't prove the vaccine was responsible for the drop-off in mumps cases. It's always possible the outbreak had already hit its peak and was on the decline anyway. They emphasized that the study doesn't mean everyone should get a third dose of the MMR vaccine. But in outbreaks, booster shots could be one tool when other infection-control strategies fail, they said.

"We have learned that providing a third dose may be effective in stopping an outbreak," Kutty said.

Dr. Saad Omer, from the Emory Vaccine Center in Atlanta, said that's an important lesson for dealing with future mumps outbreaks, both in the U.S. and elsewhere.

"The vaccine is so safe and the evidence is very reasonable now," Omer, who wasn't involved in the new study, told Reuters Health. "I think (a third vaccine) should be on the list of first-line options for decent-sized outbreaks."

Mumps outbreaks are most common in crowded settings such as college dorms and prisons, he added. So the recent outbreak in religious schools "is not all that unique."

Pediatrician and vaccine researcher Dr. Amanda Dempsey from the University of Colorado Denver said the Orange County outbreak was probably due to a combination of big families and crowded schools as well less than 100-percent MMR vaccine coverage.

She, as well as the study's authors, said the report also highlights the importance of following vaccination recommendations in early childhood.

The boy who first introduced mumps into the Catskill Mountain camp had himself contracted the disease during an outbreak in Britain, where concerns over vaccine safety had led to low vaccination rates. The boy had previously received the standard two doses of mumps vaccine.

"The main way that vaccine-preventable diseases get propagated is through people who aren't fully vaccinated," Dempsey said. "Even small drops in vaccine coverage can have major implications."

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By Rachael Rettner
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The number of measles cases and outbreaks spiked last year, with unvaccinated people making up the majority of those affected, according to a new report from the Centers for Disease Control and Prevention.

In 2011, there were 222 cases of measles in the United States. That's the highest number reported measles cases in the united states in 15 years, said Dr. Anne Schuchat, director of CDC's Office of Infectious Diseases, speaking to reporters today.

The number is also more than triple the number of cases in 2009 and 2010, according to the report.

About half of the 2011 cases occurred during outbreaks, which are defined as at least three cases that are linked to each other. Last year, there were 17 measles outbreaks, well above the average of four for the previous decade.

Among patients who were U.S. residents, 72 percent of cases developed in people who had not received the measles vaccination, or had unknown vaccination history, despite being eligible for the vaccine. (Twenty-six cases occurred in people living outside the U.S.)

Fifty patients were children between 16 months and 19 years old who had not been vaccinated for philosophic or religious reasons or personal objections, the report says.

Since 2000, measles has been considered eliminated in the United States. The disease occurs here mostly when people become infected after traveling to other countries and transmit the disease to others upon their return. Indeed, 90 percent of the cases in 2011 had their origins in other countries, including 52 U.S. citizens who became ill after traveling abroad.

"The increase in measles importations and outbreaks during 2011 serves as a reminder that measles remains endemic in many parts of the world and unvaccinated U.S. residents continue to place themselves and others in their communities at risk for measles and its complications," the report says.

In 2011, more than 30,000 cases of measles were reported in European countries, with France, Italy, Romania, Spain and Germany having the majority of cases.

The measles, mumps and rubella vaccine is recommended for all children ages 12 to 15 months, with a booster shot at age 4 to 6 years. Children as young as 6 months can recieve the vaccine if there are plans for the family to travel abraod. Adults should be vaccinated if they did not recieve the vaccine when they were younger.

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