Outbreaks of mumps have been all too common on college campuses in recent years. In late 2016, close to 200 students fell ill at the University of Missouri, There were 63 cases around that time at the State University of New York in New Paltz. Smaller outbreaks have occurred at Harvard, Tufts, Illinois State, the University of Iowa and so forth. Many weeks of the academic year seem to bring new reports of mumps outbreaks, even among fully vaccinated students.
The full cause isn’t known. Some have pointed out that because so many students are vaccinated for mumps, it makes sense that they would represent a large number of those to fall ill. The mumps vaccine is highly effective, but still, about 12 percent of vaccinated people who are exposed to mumps will become sick. That means that if 95 percent or more of students at a college are vaccinated, they’re going to represent a significant number of those who fall ill – but they are still far more protected than unvaccinated students. If most students weren’t vaccinated, these outbreaks would quickly become epidemics.
A few people have hypothesized that perhaps new strains of mumps were emerging and that the current vaccine could not provide adequate protection.
But a recent Harvard study provides support for a third possibility: That the vaccine’s protection wears off with time, and all that’s needed is a third dose.
This conclusion meshes with the fact that the increase in outbreaks during the past 12 years has occurred more among young adults in college than among younger students at middle and high schools. It’s also in keeping with a the most recent recommendations from the Advisory Committing for Immunization Practices, a panel of the U.S. Centers for Disease Control and Prevention that meets regularly to review and update vaccine schedules and use. In February, ACIP suggested an additional mumps vaccine for adults who are “in an outbreak setting.”
The Harvard study suggests that perhaps a regularly scheduled dose at around age 18 would be helpful.
“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,” said Yonatan Grad, assistant professor of immunology and infectious diseases at Harvard Chan School, who co-authored the study. It was published in the March 21 issue of Science Translational Medicine.
Mumps infections can result in serious side effects including meningitis and deafness as well has testicular inflammation, which can cause infertility. Public health officials have pointed out that the vaccine reduces the chances of these side effects, even in those who catch mumps.
According to a press release from the Harvard T.H. Chan School of Public Health, the mumps vaccine was introduced in the mid-1960s and resulted in dramatic drops in mumps cases in the United States. In 1989, a second vaccine for mumps was recommended, with the hope that this might eliminate the disease from the country.
“But recent mumps outbreaks, including on college campuses, began occurring among vaccinated young adults around 2006 and have continued to the present,” the press release says.
The Harvard researchers analyzed data from six previous studies of mumps vaccine effectiveness that had been conducted in the United States and Europe. They estimated that 25 percent of vaccinated Americans may lose protection within eight years, and half might lose that protection within 19 years – which would account for the outbreaks in college-age students. In addition, students live in close quarters where communicable diseases might be spread more easily.
The researchers found no evidence that new strains of mumps virus are involved in the recent college outbreaks; if that were true, they said, there would be more outbreaks among children.
A report on the new study by Science magazine said that not all scientists are convinced that the wearing off of effectiveness is the only reason for the college outbreaks, though they agree that a third vaccination might be a good idea.
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