Recent mumps outbreaks in the US have primarily occurred in highly vaccinated populations in close-contact settings, with most cases occurring among vaccinated young adults, a recent study found. Researchers assessed the epidemiological characteristics of mumps outbreaks with ≥20 cases reported in the US from July 2010 through December 2015. They found:
- 23 outbreaks with 20-485 cases/outbreak were reported in 18 jurisdictions.
- Median duration of outbreaks was 3 months.
- All outbreaks involved close-contact settings (78% universities, 70% occurred primarily among young adults, 39% occurred in highly vaccinated populations [2-dose measles-mumps-rubella vaccine coverage >85%]).
- Most cases occurred among vaccinated young adults (median age 18-24 years), suggesting waning immunity played a role.
Clemmons N, Redd SB, Gastanaduy PA, Marin M, Patel M, Fiebelkorn AP. Characteristics of large mumps outbreaks in the United States during July 2010–December 2015. [Published online ahead of print September 10, 2018]. Clin Infect Dis. doi:10.1093/cid/ciy779.
Over the past few years there have been more mumps outbreaks in the United States as highlighted by this article. This article raises the question of declining mumps immunity with time. This year in January, the ACIP stated that during an outbreak a patient at risk for mumps may get a 3rd dose of an MMR. Because most patients received their 2 doses of MMR prior to entry of school, it also may be possible at some time in the future that we may be administering a 3rd dose of the MMR to all patients in late adolescence. We will have to wait and see how these episodic epidemics play themselves out to make this decision. It also underscores the importance of having a high vaccination rate in the entire population to help decrease epidemics that would impact vaccinated patients with weaning immunity. —John Russell, MD