Study: Mumps outbreaks linked to vaccine losing efficacy

Study: Mumps outbreaks linked to vaccine losing efficacy
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A string of outbreaks of the mumps virus in Europe and the United States is linked to waning effectiveness of the vaccine, according to a study published Wednesday in Science Magazine.

Study authors Joseph Lewnard and Yonatan Grad write that because the mumps virus has seen a resurgence among older individuals in communities with high-vaccination coverage, the evidence points to the vaccine losing some effectiveness 27 years after inoculation.

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"Outbreaks affecting vaccinated individuals and communities with high vaccine coverage have prompted concerns about the effectiveness of the live attenuated vaccine currently in use," they write.

The mumps vaccine, first developed in 1948, is applied once between 12 months and 15 months and again when the child is 4 to 6 years old. The Centers for Disease Control and Prevention (CDC) estimates the long-term effectiveness of one dosage at 78 percent, and two doses at 88 percent.

The new study recommends a third dosage of the vaccine to be applied at age 18, and suggests that clinical trials begin to study the effectiveness of revaccination.

"Routine use of a third vaccine dose at 18 years of age, or booster dosing throughout adulthood, may be a strategy to prevent mumps re-emergence and should be assessed in clinical trials," they wrote.

Lewnard told CNN in an interview Wednesday that they expect 25 percent of individuals vaccinated with the mumps vaccine to be at risk of contracting the virus within just eight years of the shot, and added that it varies by patient.

"We estimated that protection lasts on average 27 years," Lewnard said. "We estimate that about 25 percent of people will lose protection and be at risk for mumps in about eight years and that 50 percent will be at risk in about 19 years, and 75 percent of people will be at risk within 38 years. So the timing at which people lose protection can definitely vary individually."