Science Translational Medicine
21 March 2018 Vol 10, Issue 433
Vaccine waning and mumps re-emergence in the United States
By Joseph A. Lewnard, Yonatan H. Grad
Science Translational Medicine21 Mar 2018 Restricted Access
The estimated waning rate of vaccine-conferred immunity against mumps predicts changes in the ages of U.S. mumps cases seen over the past five decades.
The mystery of mumps resurgence
Rising mumps cases in vaccinated populations in the United States over the past decade have raised doubts about mumps vaccine efficacy. Here, Lewnard et al. examined these outbreaks using mumps vaccine effectiveness data and dynamic transmission modeling. They found that the increase in mumps cases is more consistent with loss of vaccine protection over time, rather than incomplete protection against an evolving virus population or lack of immune response to the vaccine. Their work also suggested that a third vaccine dose may extend protection, which could prove useful in designing a clinical action plan to prevent the spread of mumps.
After decades of declining mumps incidence amid widespread vaccination, the United States and other developed countries have experienced a resurgence in mumps cases over the last decade. Outbreaks affecting vaccinated individuals and communities with high vaccine coverage have prompted concerns about the effectiveness of the live attenuated vaccine currently in use. It is unclear whether immune protection wanes or whether the vaccine protects inadequately against currently circulating mumps virus lineages. Synthesizing data from six studies of mumps vaccine effectiveness, we estimated that vaccine-derived immune protection against mumps wanes on average 27 years (95% confidence interval, 16 to 51 years) after vaccination. After accounting for this waning, we found no evidence that the emergence of heterologous virus genotypes contributed to changes in vaccine effectiveness over time. A mathematical model of mumps transmission confirmed the central role of waning immunity to the vaccine in the re-emergence of mumps cases. Outbreaks from 2006 to the present among young adults, and outbreaks in the late 1980s and early 1990s among adolescents, aligned with peaks in mumps susceptibility of these age groups predicted to be due to loss of vaccine-derived protection. In contrast, evolution of mumps virus strains escaping immune pressure would be expected to cause a higher proportion of cases among children, not adolescents and young adults as observed. Routine use of a third vaccine dose at 18 years of age, or booster dosing throughout adulthood, may be a strategy to prevent mumps re-emergence and should be assessed in clinical trials.