Campaign Mode MMR Vaccination to Control Outbreak of Mumps in a Highly Vaccinated Population: Evidence-based Medicine viewpoint.

Abstract

This study evaluated the effectiveness of a third dose of MMR vaccine for outbreak control, and assessed for waning immunity. Of 20,496 university students who were enrolled during the 2015–2016 academic year, mumps was diagnosed in 259 students. Fisher’s exact test was used to compare unadjusted attack rates according to dose status and years since receipt of the second MMR vaccine dose, and multivariable time-dependent Cox regression models were used to evaluate vaccine effectiveness, according to dose status (3 doses vs 2 doses, and 2 doses vs 0 dose) after adjustment for the number of years since the second dose. The attack rate was lower among the students who had received three doses than among those who had received two doses (6.7 vs 14.5 cases per 1000 population, P<0.001). Students had more than 9-times the risk of mumps if they had received the second MMR dose 13 years or more before the outbreak. At 28 days after vaccination, receipt of the third vaccine dose was associated with a 78.1% lower risk of mumps than receipt of a second dose (adjusted hazard ratio, 0.22; 95% CI 0.12 to 0.39). The vaccine effectiveness of two doses versus no doses was lower among students with more distant receipt of the second vaccine dose. The authors concluded that students who had received a third dose of MMR vaccine had a lower risk of mumps than those who had received two doses. Students who had received a second dose of MMR vaccine 13 years or more before the outbreak had an increased risk of mumps.