Mumps outbreaks are on the rise among young adults likely because of waning vaccine protection, according to a new study published in the journal Science Translational Medicine.
Since 2006, mumps outbreaks have grown, with 304 cases confirmed in the U.S. already this year and 122 in the U.K. Researchers from Harvard University found the resurgence to be "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."
A booster shot at 18, or booster dosing through adulthood, might be a strategy to prevent the disease's reemergence, "and should be assessed in clinical trials," write study authors Joseph Lewnard, a postdoctoral research fellow with the Harvard School of Public Health's Center for Communicable Disease Dynamics, and Yonatan H. Grad, assistant professor of immunology and infectious diseases at Harvard Chan School.
The mumps vaccine was introduced in the mid-1960s, and annual cases of the illness decreased by 99 percent, according to the Centers for Disease Control and Prevention. The 1980s brought more outbreaks, though, and health experts added another mumps, measles and rubella (MMR) shot for children ages four to five onto recommendations.
In 2006, outbreaks happened again, this time concentrated around prisons, college campuses and close-knit communities, according to the U.K.'s Daily Mail.
"Outbreaks affecting vaccinated individuals and communities with high vaccine coverage have prompted concerns about the effectiveness of the live attenuated vaccine currently in use," write the authors.
For the study, Lewnard and Grad analyzed data from six studies of mumps vaccine effectiveness conducted in the U.S. and Europe, and found immunization against the illness lasts an average of 27 years following the final vaccine.
The pair also estimated 25 percent of Americans vaccinated against mumps as children might lose protection within about eight years, 50 percent within 19 years, and 75 percent within 38 years.
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