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The U.S. Centers for Disease Control and Prevention (CDC) currently recommends that children get two doses of MMR vaccine; the first dose is recommended between the ages of 12 and 15 months, and the second dose between 4 and 6 years.1
In the U.S., vaccination rates for MMR are high, with more than 91 percent of 19- to 35-month-olds having received one or more doses.2 However, the mumps portion of the vaccine is not 100 percent effective.
According to the CDC, even after two doses the mumps component is only about 88 percent effective, with a range of 66 percent to 95 percent. Effectiveness after one dose is about 78 percent, with a range of 49 percent to 92 percent.3
As the CDC explained, "Mumps outbreaks can still occur in highly vaccinated U.S. communities, particularly in close-contact settings such as schools, colleges and camps," and that's precisely what we're seeing with the most recent outbreaks.
Mumps Outbreaks Occurring in Highly Vaccinated Communities
In 2016, there were 5,311 cases of mumps reported in the U.S. — the most since 2006, when more than 6,500 cases were reported. A spike in cases also occurred in 2009, and so far in 2017 more than 1,000 cases have been reported.4
Most of the outbreaks occurred among young adults — college or high-school students. As The Washington Post noted, "The mumps outbreaks have been occurring in communities with high rates of ... [vaccination] and residents who often have received both recommended doses of the vaccine."5
Even the CDC stated, " ... 2-dose vaccine failure and possible waning of vaccine-induced immunity have been described in recent outbreaks, particularly in high-density, close-contact settings."6
For instance, in 2016, 41 students at Harvard University came down with mumps and, according to the Public Health department in Cambridge, every single one of those students had been vaccinated.7
In Toronto, meanwhile, public health officials reported an outbreak of 17 mumps cases occurring in 18- to 35-year-old individuals, many of whom had visited the same area of bars.
A handful of additional mumps cases were also reported across Canada, including four cases in Edmonton and eight cases among a hockey team in Medicine Hat, a city in Alberta, Canada.8,9
Toronto Public Health spokeswoman Lenore Bromley told The Canadian Press that the risk to the general public was low, yet public health officials were still urging Canadians to check their vaccination records and consider a booster dose of MMR vaccine.10
US Health Officials Considering a Third MMR Vaccine
The U.S. Advisory Committee on Immunization Practices (ACIP) has formed a mumps work group to discuss whether a third MMR vaccine should be added to the U.S. childhood vaccine schedule.
Their recommendations are not expected to be released until February 2018, as they're expected to review a number of issues, including whether protections offered by the vaccine wane over time.
Also at issue is the fact that mumps is only available as a combined MMR vaccine, so giving an additional dose of mumps vaccine also means giving an additional dose of measlesand rubella vaccines.
ACIP liaison member Patsy Stinchfield told The Huffington Post that, "in general, receiving extra doses of MMR vaccine is not ideal."11 Some areas have already started recommending a third dose during outbreaks. Such is the case in Arkansas, where 2,800 mumps cases have occurred since 2016.12
In 2015, the Illinois Department of Public Health (IDPH) also recommended a third MMR dose to students at the University of Illinois at Urbana-Champaign, when more than 300 students developed mumps (another outbreak among a highly-vaccinated population).13
Will Adding a Third Dose of MMR Stop Mumps Outbreaks?
The CDC even has guidelines in place for when public health agencies may want to advise residents to get a third dose — even though evidence of the effectiveness of this strategy is lacking. As it is, the consideration for the third dose is coming after widespread failure rates of the two-dose regimen.
According to the CDC, "Because outbreaks occur despite high two-dose coverage, a third dose has been provided as a control measure to targeted populations during previous outbreaks."14
Adding yet another dose of an already failing vaccine seems highly questionable, however, especially in light of evidence that its effectiveness may have been exaggerated to begin with. According to the National Vaccine Information Center (NVIC):
"In 2012, new information questioning the efficacy of the mumps portion of MMR vaccine emerged when two former Merck employees filed a lawsuit alleging the company altered testing results and studies to make the mumps vaccine in MMR appear to be more effective than it really is in preventing mumps infection."Meanwhile, outbreaks of measles have also been reported, despite a very highly vaccinated U.S. population.
Some have suggested adding a third MMR vaccine to eradicate measles as well, but emerging scientific evidence suggests it never will be completely eliminated15 — no matter how many doses of MMR vaccine are mandated for every man, woman and child in the world — and the same may be true of mumps.
What we do know is that the MMR vaccine clearly does not work for everyone. In 2014, researchers investigated a mumps outbreak among a group of students in Orange County, New York.
Of the more than 2,500 who had received two doses of MMR vaccine, 13 percent developed mumps, and the researchers concluded "two doses of mumps-containing vaccine may not be as effective in outbreak settings with multiple, prolonged and intense exposure."16
How Dangerous Is Mumps?
Mumps is a viral illness spread via saliva and respiratory droplets. It's spread by coughing and sneezing, sharing contaminated objects (like eating utensils) or touching contaminated objects or surfaces.
Symptoms include fever, headache, muscle aches and fatigue, along with characteristic swelling of the salivary glands under the ears, leading to swollen and puffy cheeks and jaw.
In occasional cases, mumps can lead to complications including meningitis, encephalitis (inflammation of the brain), deafness, inflammation of the ovaries and/or breast tissue and inflammation of the testicles, which rarely may lead to sterility.17
However, according to the CDC, "Some people who get mumps have very mild or no symptoms, and often they do not know they have the disease. Most people with mumps recover completely in a few weeks."18
The head of the ACIP's work group on mumps, Kelly Moore, also stated that the recent mumps outbreaks have not been serious.19
What Are the Risks of MMR Vaccine?
If a vaccine is indeed highly effective, and avoiding the disease in question is worth the risk of the potential side effects from the vaccine, then many people would conclude that the vaccine's benefits outweigh the risks. They may even be in favor of an additional dose.
However, if the vaccine is ineffective, and/or if the disease doesn't pose a great threat to begin with, then the vaccine may indeed pose an unacceptable risk. This is particularly true if the vaccine has been linked to serious side effects.
Unfortunately, that's the case with the MMR vaccine, which has been linked to thousands of serious adverse events and hundreds of deaths.
According to NVIC, "As of September 1, 2015, there had been 10 claims filed in the federal Vaccine Injury Compensation Program (VICP) for injuries and deaths following MMR vaccination." In addition, NVIC reported:20
Could the Mumps Virus Have Mutated?"Using the MedAlerts search engine, as of September 30, 2015, there had been 7,508 serious adverse events reported to the Vaccine Adverse Events Reporting System (VAERS) in connection with MMR vaccines since 1990.Over half of those serious MMR vaccine-related adverse events occurred in children 3 years old and under. Of these MMR-vaccine related adverse event reports to VAERS, 360 were deaths, with over 60 percent of the deaths occurring in children under 3 years of age."
There are a number of different mumps virus strains used by different vaccine manufacturers in different countries. The U.S. uses the Jeryl-Lynn strain in the MMR vaccine developed by Merck. There's significant disagreement among scientists and health officials about whether the mumps virus is evolving to evade the vaccine or whether the issue is simply waning immunity (or perhaps both).
However, according to Dr. Dirk Haselow, an epidemiologist with the Arkansas Department of Health, the attenuated mumps virus strain in the current MMR vaccine may not even match the disease they're now seeing in some patients:21
A 2014 paper written by U.S. researchers developing a new mumps vaccine also suggested that a possible cause of mumps outbreaks in vaccinated persons in the U.S. could be due to "... the antigenic differences between the genotype A vaccine strain and the genotype G circulating wild-type mumps viruses."22"We are actually to the point that we are worried that this vaccine may indeed not be protecting against the strain of mumps that is circulating as well as it could. With the number of people we've seen infected, we'd expect three of 400 cases of orchitis, or swollen testicles in boys, and we've seen five."
Another concerning study published in Acta Neuropathologica in February 2017 describes the first confirmed report of vaccine-strain mumps virus (live-attenuated mumps virus Jeryl Lynn, or MuVJL) found in the brain of a child who suffered "devastating neurological complications" as a result. The researchers stated:23
"This is the first confirmed report of MuVJL5 associated with chronic encephalitis and highlights the need to exclude immunodeficient individuals from immunization with live-attenuated vaccines. The diagnosis was only possible by deep sequencing of the brain biopsy."
Clearly there is far more that needs to be understood about the MMR vaccine before a third dose is added to the already-packed childhood vaccine schedule.
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