FROM AN ACIP MEETING
Because of a spate of mumps outbreaks over the last decade, adding a third dose of the mumps vaccine to the currently standard two-dose series was debated during a meeting of the Center for Disease Control and Prevention’s Advisory Committee on Immunization Practices (ACIP).
“Data [on recent outbreaks] were presented to ACIP in 2012, and ACIP determined that the data were insufficient to recommend for or against the use of a third dose of MMR vaccine for mumps outbreak control,” explained Mona Marin, MD , of the CDC’s National Center for Immunization and Respiratory Diseases. “Subsequently, CDC issued guidance for consideration for use of a third dose in specifically identified target populations, along with criteria for public health departments to consider for decision-making. That includes settings with high two-dose coverage, intense exposure, and ongoing transmission.”
The mumps vaccine was first introduced as a single-antigen vaccine in 1967. Currently, it’s available as a combination vaccine with measles and rubella, which has an effectiveness rate of 77% with one dose, and 88% with two doses, according to information shared by Dr. Marin. However, since 2006, cases of mumps in the United States have risen, with that year on its own accounting for a disproportionately high number of mumps cases over the last decade, with more than 6,500 cases occurring in at least eight states in the midwestern United States. Many of these cases have occurred in or around colleges and universities, in populations that have been vaccinated and should therefore be protected.
Recent data, explained Dr. Marin, have “raised the question of the short- and long-term benefits of a third dose, and implications for routine use versus outbreak policy recommendations.” However, the efficacy of a third vaccine dose has not been verified against cell memory, cell-mediated response, and other factors. These will need to be evaluated before a third dose can be debated further, let alone approved.
The mumps work group, therefore, will continue to assess the benefits and potential harms of adding a third dose to the immunization schedule. Dr. Marin explained that they hope to be able to discuss this further, and perhaps vote on it, during the next ACIP meeting, which is scheduled to take place on June 21 and 22 of this year.
“The current two-dose schedule is sufficient for mumps control in the general population, but outbreaks can occur in well-vaccinated populations in specific settings,” Dr. Marin said. “Intense exposure settings and waning immunity appear to be risk factors for secondary vaccine failure. The benefit of a third MMR dose still needs to be assessed.”
Dr. Marin said she had no relevant financial disclosures.