Mumps Outbreaks Apparently Not Caused by New Viruses That Evade Existing Vaccine

FDA scientists report that the global resurgence of mumps outbreaks is not caused by mutated strains of the mumps virus evading mumps vaccine-induced immune responses.


The scientists concluded that these outbreaks reflect a progressively weakening immune response to mumps viruses that occurs over the years following childhood vaccination. Notably, recent outbreaks have targeted predominately young adults.


The finding means that the answer to this problem isn’t to develop a new vaccine to protect against new strains of mumps virus. Instead, the study opens the door to consider whether the most effective strategy would be to re-vaccinate adolescents in order to restore their immunity to these viruses.


The suggestion that re-vaccination could help prevent future mumps outbreaks is supported by the results of widespread vaccination of military recruits in the United States initiated in 1991. In that year the military began routine administration of the measles, mumps, and rubella (MMR) vaccine. Subsequently, despite being in dense living conditions, military recruits were spared involvement in recent outbreaks in the United States, while outbreaks occurred among university students who lived in close contact on campuses.


The scientists showed that the anti-mumps virus antibodies from young children vaccinated with MMR were able to neutralize a variety of strains of mumps virus. This was strong evidence mumps viruses were not changing so much that antibodies triggered by the vaccine could no longer recognize them. Instead, the immune response triggered by the initial vaccination appears to weaken over the years in some people, but can likely be rejuvenated by revaccinating people when they are adolescents.

See the FDA Announcement