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Mumps vaccine protection wanes over years; more doses recommended
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Vaccine protection against mumps with two doses weakens after 27 years on average, and a third dose at age 18 years may help prevent the disease’s re-emergence, according to researchers.
Boosters during adulthood may also extend protection against mumps, which has reappeared among widely vaccinated populations in recent years, they said.
“The ongoing resurgence in mumps among young adults has undermined previous enthusiasm about near-term elimination of this disease from the United States,” Joseph A. Lewnard, PhD, a postdoctoral research fellow, and Yonatan H. Grad, MD, PhD, an assistant professor of immunology and infectious diseases, both at Harvard University’s T.H. Chan School of Public Health, wrote in Science Translational Medicine.
Since the mumps vaccine was introduced in the U.S. in 1967, cases of the disease have decreased by more than 99%. However, outbreaks have occurred in the late 1980s and early 1990s among adolescents, and since 2006 among young adults, despite routine two-dose immunization with the measles-mumps-rubella vaccine.
Lewnard and Grad wanted to determine which factor — the time elapsed since last vaccination, or resistance by new mumps virus strains — was dulling vaccine efficacy. To estimate the potential effects of both factors, they performed a meta-analysis of six studies on mumps vaccine efficacy conducted in the U.S. and Europe.
“At issue is whether the re-emergence of mumps can be prevented by modifying vaccine dosing schedules, or whether a new vaccine must instead be developed,” the researchers wrote.
Following their meta-analysis, they estimated that mumps immunity lasts for an average of 27.4 years after any dose of the vaccine (95% CI, 16.7-51.1). Of the 96.4% of people expected to have a primary response to vaccination, the researchers said about 25% may lose immunity within 7.9 years, 50% within 19 years and 75% within 38 years.
Lewnard and Grad also sought to address the suspicion that mixed virus genotypes emerging after vaccine introduction in 1967 might diminish vaccine efficacy. They said they found no evidence that efficacy had declined between 1965 and 2006, “in particular after controlling for the effect of vaccine waning.”
The researchers added that — by their modeling — newer, vaccine-resistant virus strains would be expected to affect younger children disproportionately, but that did not occur in most recent outbreaks.
They suggested that a routine third dose of the vaccine at age 18 years could extend protection against mumps through early adulthood, protecting an age group often affected in recent outbreaks. A booster administered every 10 years thereafter would render at least 68% protection if vaccine coverage was 88%, the researchers estimated. At the same coverage rate, a booster every 20 years would result in at least 55.2% protection, they added.
As the number of older adults with immunity from prior mumps infection decreases, vaccine protection in the remaining population will become the key factor in controlling the disease, the researchers said.
“We expect population susceptibility to mumps to continue increasing as transient vaccine-derived immunity supersedes previous infection as the main determinant of mumps susceptibility in the U.S. population,” they wrote. “These observations indicate the need for innovative clinical trial designs to measure the benefit of extending vaccine dosage schedules or new vaccines to address the problem of waning vaccine-induced protection.” – by Joe Green
Disclosures: Lewnard reports that he has received grant funds from Pfizer, which were given to Harvard University, and that he has consulted for Pzifer in work unrelated to this study. Grad reports that he has consulted for GlaxoSmithKline in work unrelated to this study.
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