HOUSTON – The Unites States mumps vaccination program was started in 1967, according to the Centers for Disease Control and Prevention.
Around that time, the CDC said more than 185,000 cases were reported annually, but it said the actual number of cases was likely much higher due to underreporting.
Mumps outbreaks can still occur in highly vaccinated communities, the CDC says.
"A major factor contributing to outbreaks is being in a crowded environment, such as attending the same class, playing on the same sports team, or living in a dormitory with a person who has mumps," the CDC says on its website.
Outbreaks can happen at any time of the year and are more likely in close-contact settings.
Vaccination helps limit the size, duration and spread of mumps outbreaks, the CDC says.
"(Measles, mumps and rubella) vaccine prevents most, but not all, cases of mumps and complications caused by the disease. Two doses of the vaccine are 88 percent (range: 66 percent to 95 percent) effective at protecting against mumps; one dose is 78 percent (range: 49 percent to 92 percent) effective. Studies have shown that the MMR vaccine protects against currently circulating mumps strains," the CDC says.
Since the prevaccination era, mumps cases in the United States have decreased by 99 percent, but in recent years, there has been an increase in mumps cases.
According to the CDC, in 2012, 229 mumps cases were reported and in 2016, 6,366 cases were reported.
It is not mandatory to report mumps cases to the CDC, but many health departments will contact the CDC when they experience a high number of cases.
In 2016 and 2017, a number of outbreaks were reported, mostly on college campuses.
Here is a look at some of the past mumps outbreaks, according to the CDC:
- In 2016-17, a large outbreak in a close-knit community in northwest Arkansas resulted in nearly 3,000 cases.
- In 2015-16, outbreaks were reported from several university campuses, including a number of smaller outbreaks with limited spread. The two largest outbreaks were from Iowa and Illinois, each involving several hundred university students; both held wide-scale vaccination campaigns.
- In 2014, several outbreaks affiliated with universities were reported from multiple states, including one community outbreak in Ohio linked to a university that involved over 400 people and an outbreak affecting the National Hockey League.
- In 2011-13, there were several smaller mumps outbreaks reported on college campuses in California, Virginia and Maryland. However, these all had limited spread, and national case counts for these years were at several hundred cases per year.
- In 2009-10, two large outbreaks occurred.
- One multiyear outbreak involved over 3,000 people and mostly affected high school-aged students who were part of a close-knit religious community in New York City and attended schools in which they had very close contact. The outbreak started when an infected student in this religious community returned from the United Kingdom where a large mumps outbreak was occurring.
- The second outbreak involved about 500 people, mostly school-aged children, in the U.S. territory of Guam.
- In 2006, the United States experienced a multistate mumps outbreak involving more than 6,500 reported cases. This resurgence predominantly affected college-aged students living in the Midwest, with outbreaks occurring on many different Midwestern college campuses.