Mumps Outbreak in a Highly Vaccinated University-Affiliated Setting Before and After a Measles-Mumps-Rubella Vaccination Campaign-Iowa, July 2015-May 2016.

Background: In response to a mumps outbreak at the University of Iowa and surrounding community, university, state, and local health officials implemented a vaccination campaign targeting students <25 years of age with an additional dose of measles-mumps-rubella (MMR) vaccine. More than 4700 vaccine campaign doses were administered; 97% were documented third doses. We describe the epidemiology of the outbreak before and after the campaign, focusing on cases in university students.

Methods: Mumps cases were identified from reportable disease databases and university health system records. Detailed information on student cases was obtained from interviews, medical chart abstractions, university and state vaccination records, and state public health laboratory results. Pre- and postcampaign incidence among students, university faculty/staff, and community members <25 vs ≥25 years old were compared using Fisher exact test. Multivariable regression modeling was performed to identify variables associated with a positive mumps polymerase chain reaction test.

Results: Of 453 cases in the county, 301 (66%) occurred in university students. Student cases were primarily undergraduates (90%) and highly vaccinated (86% had 2 MMR doses, and 12% had 3 MMR doses). Fewer cases occurred in students after the campaign (75 [25%]) than before (226 [75%]). Cases in the target group (students <25 years of age) declined 9% postcampaign (P=.01). A positive mumps polymerase chain reaction test was associated with the presence of parotitis and early sample collection, and inversely associated with recent receipt of MMR vaccine.

Conclusions: Following a large additional dose MMR vaccination campaign, fewer mumps cases occurred overall and in the target population.