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Mumps - Outbreak Q&A

For Parents and Healthcare Professionals

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How many cases usually occur in the US each year?
In the United States, since 2001, an average of 265 mumps cases (range: 231-293) have been reported each year. (See related MMWR article: MMWR Dispatch—Mumps Epidemic-Iowa, 2006 March 30, 2006 [55(13);366-368])

When did the outbreak in the Midwest start?
The first cases of mumps-like illness were reported from Iowa in December 2005. More cases have been occurring since then in Iowa, and in several other states. (See 2006 Mumps Outbreak page)

Where did the outbreak in the Midwest start?
The current information indicates that the outbreak may have begun on a college campus. Colleges that have group living, dining, studying, and sports areas that make disease transmission more likely, and increase the chance of outbreaks. Once started, such outbreaks sometime spread to the community, causing illness in persons who do not attend college. For this reason, CDC recommends that all college students have two doses of measles-mumps-rubella (MMR) vaccine. Studies have suggested that strict enforcement of these recommendations is important for preventing and stopping outbreaks.

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Why are people who have been vaccinated getting sick?
One dose of mumps vaccine prevents approximately about 80% of mumps and two doses approximately about 90% of cases. Even though the vaccine is effective, if most persons in a population are vaccinated, most cases in an outbreak would also be expected to be vaccinated. However, if the vaccine hadn't been used, the outbreak would have affected everyone, rather than a small percent of the population.

Does the current vaccine work against the mumps virus that is causing the outbreak?
Yes. The strain of mumps virus in the Midwest is the same as the one that is found in other countries, and that caused a large ongoing outbreak in the United Kingdom (UK) with more than 60,000 cases. In 2005 a small mumps outbreak occurred in the US after a person visited from the UK and mumps vaccine was effective in controlling this outbreak.

Have there been other mumps outbreaks?
Yes. There has been an ongoing mumps outbreak in the United Kingdom (UK). This outbreak was mostly among unvaccinated young adults, 3.3% of them had 2 doses of mumps vaccine, and 30.1% had one dose of mumps vaccine. (See related MMWR article.)

There was a mumps outbreak in a camp in New York in 2005 that was believed to have begun after a camp counselor from the UK developed mumps.
(See related MMWR article.)

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Will there be an outbreak in the school I or my child attends?
Many different things affect whether or not an outbreak of mumps might begin in a school, but outbreaks can only begin when there are enough people in an area (school or community) who are not immune from the disease. The best way to prevent a mumps outbreak in a school is to make sure that everyone in that school has had two doses of mumps vaccine (MMR).

What can be done to stop the spread of mumps?
Anyone with mumps should not go back to child care, school or work for 5 days after symptoms begin. People who come in contact with a mumps case should have their immunization status evaluated. Anyone who has not received mumps-containing vaccine (preferably MMR vaccine) should be vaccinated. The local health department or a physician can help determine if a person needs one or two doses of MMR vaccine. Persons who may have been in contact with a mumps case should be educated on the signs and symptoms of mumps disease and should seek medical attention if any of these symptoms begin.

In an outbreak, should people born before 1957 get the vaccine--I heard people that age were immune?
As noted in the Health Advisory released April 14, 2006, birth before 1957 is generally accepted as proof of mumps immunity. But birth before 1957 does not guarantee mumps immunity. So, in an outbreak, vaccinating persons born before 1957 with 1 dose of MMR should be considered if the epidemiology of the outbreak suggests increased risk of disease in persons of this age.

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Is the MMR vaccine safe for elderly persons?
Yes, the MMR vaccine is safe for most elderly persons; some with certain medical problems should not get the vaccine. Most elderly persons are probably immune to mumps because they had mumps as a child. However, if this group is affected by the outbreak, vaccinating elderly persons with 1 dose of MMR should be considered.

Should an infant receive MMR to prevent mumps before age 12 months?
No. The MMR vaccine has not been studied extensively in infants who are not 1 year old yet. Antibody from the mother may protect the infant during the first year of life, but this wears off during the first year.

How many doses of MMR do children need?
Children should receive 2 doses of MMR vaccine. Infants should be vaccinated with the first dose as close to the first birthday as possible. The second dose is routinely recommended for ages 4–6.

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Can I get my child's second MMR dose before age 4?
Yes. The second dose is routinely recommended for ages 4-6; but, vaccinating before age 4 should be considered if the epidemiology of the outbreak suggests increased risk of disease among young children. The second dose of MMR can be given any time after the first dose a long as 28 days have passed since the first dose. Talk with your healthcare provider about the need to get dose 2 of MMR for a child before age 4.

I am concerned about the news of this outbreak. What can I do?
Check with your health care provider to make sure that you and your family have been fully vaccinated. The vaccine is safe. Before vaccine was available, almost every person got the mumps. Today, in communities where vaccination rates are high, the number of people getting mumps is very low compared to the time before vaccine. In those who get mumps, serious side effects are rare.

For technical information on mumps, please refer to the Mumps–Technical FAQs page.

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