By Philip R. Fischer, MD, DTM&H

Professor of Pediatrics, Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN

Dr. Fischer reports no financial relationships relevant to this field of study.

SYNOPSIS: Mumps immunity wanes over time, with a notable increase in risk of infection 13 or more years after completion of the currently recommended series of vaccines. During an outbreak of mumps, receipt of an extra (third, by American schedules) vaccine significantly reduces the risk of becoming sick with mumps.

SOURCE: Cardemil CV, Dahl RM, James L, et al. Effectiveness of a third dose of MMR vaccine for mumps outbreak control. N Engl J Med 2017;377:947-956.

With widespread measles-mumps-rubella (MMR) vaccination in the United States, mumps has become uncommon. However, there have been five outbreaks involving thousands of cases during the past 13 years. Many of these outbreaks have centered on university campuses, where more than 90% of students had received the recommended two-dose MMR series.

Public health specialists documented outcomes during a “natural experiment” of a mumps outbreak at the University of Iowa during the 2015-2016 academic year. There were 20,496 students enrolled at the time. Overall, 98.1% of the students had received at least two MMR vaccines prior to that school year. Because of the mumps outbreak, widespread vaccination was initiated, even in individuals who previously had been “fully” vaccinated. A total of 4,783 people received an MMR vaccine. During the outbreak, 256 university students developed mumps; students accounted for two-thirds of all mumps cases seen in that geographical area during that academic year.

Students who received a third vaccine dose had an infection rate of 6.7 per 1,000 people, only about half the 14.5 rate seen in those who had received only two doses. If the second MMR had been given 13 or more years before the outbreak, there was a nine-fold increased risk of mumps infection if the third dose was not given during the outbreak.

The authors concluded that waning post-vaccine immunity was probably at least partially responsible for the propagation of the mumps outbreak. They also noted that the vaccine administration campaign providing a third dose of MMR vaccine improved outbreak control. It also is likely that a strong program of testing and case detection, as well as isolation of affected individuals, contributed to the resolution of the outbreak.

COMMENTARY

Vaccines are not perfect, even though they save lives and prevent lots of bothersome illness. The careful documentation of the effectiveness of mumps vaccination during an outbreak on a university campus is illustrative and informative. Especially when people are at risk of mumps exposure more than 12 years after completing the two-dose MMR vaccination series, they can be helped by receiving a third dose of vaccination.

So, should all students entering university receive an additional/third dose of MMR vaccine? That likely would be effective, but the costs of vaccination and of administration programs could be prohibitive. And, even though we hear about outbreaks of mumps on university campuses every one to three years, only a small minority of campuses have been affected.

After a large campus outbreak of mumps in Illinois, the Centers for Disease Control and Prevention (CDC) discussed a third MMR dose during outbreaks but did not have adequate effectiveness data to formalize a recommendation.1 The Iowa experience provides that previously missing data. Thus, in late October 2017, the Advisory Committee on Immunization Practices proposed to the full CDC that a third dose of MMR vaccine be given to people deemed to be at risk of mumps during outbreaks, even if they previously received two MMR doses; the final CDC endorsement of this proposal is pending.2

Of course, mumps is not just an American problem. Investigators in France reviewed mumps outbreaks in military barracks and university campuses.3 They noted that many cases were in individuals who had received the recommended two MMR vaccine doses, and that immunity waned after vaccination. In fact, there was a 10% increase in mumps risk each year after receipt of the second vaccine dose.3 Based on these data, the French High Council of Public Health recommended in 2013 that a third MMR dose be given during outbreaks for those whose second dose was more than 10 years prior.4 With the Iowa data showing effectiveness, the United States now is making a similar recommendation to what the French proposed four years ago, although the U.S. recommendation in its current draft form does not depend on the length of time since the second MMR.

International travel also is a risk factor for outbreaks and cases of measles and rubella, in addition to mumps.5,6,7 Children, college students, and adults should be appropriately current on routine vaccination (as well as specific travel-related vaccines) prior to international travel.8,9,10 Now, based on the Iowa data and pending CDC recommendation, people traveling to areas with active mumps outbreaks would be advised to get an “extra” third MMR dose.

REFERENCES

  1. Albertson JP, Clegg WJ, Reid HD, et al. Mumps outbreak at a university and recommendation for a third dose of measles-mumps-rubella vaccine – Illinois, 2015-2016. MMWR 2016;65:731-734.
  2. Jenco M. ACIP: Give 3rd mumps vaccine dose during outbreaks. AAP News, Oct. 26, 2017. Available at: http://www.aappublications.org/news/2017/10/26/Mumps102617. Accessed Nov. 3, 2017.
  3. Vygen S, Fischer A, Meurice L, et al. Waning immunity against mumps in vaccinated young adults, France 2013. Euro Surveill 2016;21:30156.
  4. Haut Conseil de la Santé Publique (HCSP). Avis relatif à la conduite à tenir en case d’épisodes de cas groupés d’oreillons en collectivité. Paris: HCSP; 11 Jul 2013. [Opinion on the conduct to adopt in the face of episodes of clusters of mumps in institutions]. French. Available at: http://www.hcsp.fr/Explore.cgi/avisrapportsdomaine?clefr=364. Accessed Nov. 3, 2017.
  5. Collier MG, Cierzniewski A, Duszynski T, et al. Measles outbreak associated with international travel, Indiana, 2011. J Pediatr Infect Dis Soc 2013;2:110-118.
  6. Robyn M, Dufort E, Rosen JB, et al. Two imported cases of congenital rubella syndrome and infection-control challenges in New York State, 2013-2015. J Pediatr Infect Dis Soc 2017; doi: 10.1093/jpids/pix028.
  7. Centers for Disease Control and Prevention. Mumps outbreak at a summer camp – New York, 2005. MMWR Morb Mortal Wkly Rep 2006;55:175-177.
  8. Hagmann S, LaRocque RC, Rao SR, et al. Pre-travel health preparation of pediatric international travelers: Analysis from the Global TravEpiNet Consortium. J Pediatr Infect Dis Soc 2013;2:327-334.
  9. Durham MJ, Goad JA, Neinstein LS, Lou M. A comparison of pharmacist travel-health specialists’ versus primary care providers’ recommendations for travel-related medications, vaccinations, and patient compliance in a college health setting. J Travel Med 2011;18:20-25.
  10. Hyle EP, Rao SR, Jentes ES, et al. Missed opportunities for measles, mumps, rubella vaccination among departing U.S. adult travelers receiving pretravel health consultations. Ann Intern Med 2017;167:77-84.