BOSTON — More cases of mumps are being reported nationwide, but it turns out the anti-vaxxer movement may not be the problem. A new study finds that the two vaccinations typically given during childhood eventually wear off over time.
In light of the results, health experts now recommend that everyone get an additional mumps vaccine after the age of 18. The findings are the result of a recent analysis of the infection’s resurgence among young adults in the US. Researchers at the Harvard T.H. Chan School of Public Health say that immunizations lose their potency after 27 years.
The research team extracted data from six studies examining the effectiveness of the mumps vaccine in recent decades in the U.S. and Europe. They estimated that a quarter of Americans vaccinated against the condition will lose protection in about eight years, 50% in 19 years, and 75% within 38 years.
“This analysis helps address a persistent question surrounding the recent mumps outbreaks, pointing to the key role played by waning vaccine induced immunity, and helps frame the research and policy questions on how best to control mumps,” says study co-author Yonatan Grad, an assistant professor of immunology and infectious diseases, in a university release.
Mumps incidence has been in decline since the 1960s, when the vaccine was first introduced. In 1989, a second administration of the vaccine was recommended following an outbreak among adolescents who’d only received one dose up to that point. A reduction in cases continued after that, and some thought the vaccine would wipe out the disease altogether.
Since the turn of the century, however, mumps outbreaks have returned, especially on college campuses. These outbreaks have infected vaccinated young adults, prompting many theories about the cause, from waning immune protection to vaccine-resistant strains of the mumps virus. But researchers were able to prove that the new strains had no impact on the infection’s return.
“Vaccination is the centerpiece of current public health strategy against mumps,” says co-author Joseph Lewnard, a postdoctoral research fellow at Harvard Chan School’s Center for Communicable Disease Dynamics. “Knowing that protection wanes in the long term can help inform how we deploy vaccines to prevent or contain future outbreaks.”
The full study was published in the March 21st edition of the journal Science Translational Medicine.