Study: Mumps Resurgence Due to Waning Vaccine Protection in Adults

The recent resurgence of mumps in the United States may be linked to waning vaccine protection, according to a recent analysis from Harvard TH Chan School of Public Health.¹

Despite decades of declining mumps incidence, due to widespread vaccination, recent outbreaks in vaccinated adults and communities with high vaccine coverage have prompted concerns about the effectiveness of the current vaccine. According to the CDC, from January 1 to February 24, 2018, 32 states and the District of Columbia in the United States reported mumps infection in 304 people. Outbreaks have increased from 229 cases in 2012 to 6,366 cases in 2016.²

Outbreaks are troubling, the researchers noted, because mumps infections can cause complications that can lead to infertility, meningitis, and deafness.³ With many of the cases occurring in vaccinated individuals, the researchers aimed to determine whether the resurgence is due to waning immune protection or the emergence of new strains evading the vaccine.

In the study, which was published in Science Translational Medicine, the researchers pooled and analyzed 6 epidemiological studies of mumps vaccine effectiveness conducted over past decades in the United States and Europe. The researchers estimated that vaccine-derived immune protection against mumps wanes on average 27 years after vaccination, with 25% of individuals in the United States vaccinated losing protection within 7.9 years, 50% within 19 years, and 75% within 38 years.

According to the researchers, a mathematical model of mumps transmission confirmed the central role of waning immunity to the vaccine in the recent resurgence of mumps cases, as well as in outbreaks that occurred in the late 1980s among adolescents. The researchers found no evidence that new strains of mumps virus are contributing to changes in vaccine effectiveness, as new strains would be expected to cause higher incidence among children, not adolescents and young adults.

“Vaccination is the centerpiece of current public health strategy against mumps,” Joseph Lewnard, postdoctoral research fellow at Harvard Chan School’s Center for Communicable Disease Dynamics, said in a press release about the study.³ “Knowing that protection wanes in the long term can help inform how we deploy vaccines to prevent or contain future outbreaks.”

The researchers concluded that routine use of a third vaccine dose at 18 years of age, or booster dosing throughout adulthood, may be one strategy to prevent mumps re-emergence.

The study was funded by the National Institute of General Medical Sciences award U54GM088558 and a Doris Duke Charitable Foundation Clinical Scientist Development award.

References

• Lewnard JA, Grad YH. Vaccine waning and mumps re-emergence in the United States. Science Translational Medicine. 2018. Doi: 10.1126/scitranslmed.aao5945
• Mumps Cases and Outbreaks. CDC’s website. https://www.cdc.gov/mumps/outbreaks.html. Accessed March 22, 2018.
• Mumps resurgence likely due to waning vaccine-derived immunity [news release]. Boston. Harvard’s website. https://www.hsph.harvard.edu/news/press-releases/mumps-resurgence-waning-immunity/. Accessed March 22, 2018.