Following a widespread mumps outbreak at the University of Illinois at Urbana-Champaign between April 2016-May 2016, a recent report in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly suggests that a third booster dose of the measles-mumps-rubella (MMR) vaccine may be needed.
Justin P Albertson, MS, of the Illinois Department of Public Health (IDPH) and colleagues reported that 89% of the people who contracted the illness already had 2 doses of MMR vaccine but became ill anyway.
The researchers noted that of the 317 people with mumps, 16% had 3 MMR doses, 73% had received 2 doses, 4% had a single dose, 2% were unvaccinated and 5% of cases vaccination status was unknown.
Mr Alberston and colleagues noted that “2-dose vaccine failure and possible waning of vaccine-induced immunity have been described in recent outbreaks, particularly in high-density, close-contact settings… a third dose has been provided as a control measure to targeted populations during previous outbreaks.”
Although the CDC has no formal recommendation for a third dose of MMR vaccine, federal health officials noted in the report that this instance demonstrates this strategy may be a way of controlling outbreaks. There are four criteria for recommending a third dose: mumps are seen in populations with a 2 dose vaccination rate over 90%; there is ongoing transmission for more than 2 weeks; there outbreaks is occurring in close quarter settings; and there are high infection rates of more than 5 cases per 1000 people.
Mr Albertson and colleagues said that 2 other reasons beside the above criteria demonstrated a need for a third dose of vaccine in this particular outbreak. First, researchers said it continued into what is considered “off-season” for the virus (summer), and second there was a concern for the coming fall semester when many more students would be returning to campus.
Researchers did note that the effectiveness of a third MMR dose has not been documented.
“Currently there is no formal recommendation for a third dose of MMR vaccine during mumps outbreaks; the decision to implement this intervention needs to be carefully considered. In light of the recent increased incidence of mumps, CDC is gathering additional data to assess use of a third dose of vaccine to inform decision-making during outbreak responses and potential changes in the recommendations,” the researchers wrote.