We collected information on personal characteristics (age, gender), mumps-related symptoms (using visual prompts), complications, possible previous mumps infections, contact with mumps cases, days absent from social activities, contact with health care providers and self-reported immunization status. We used a web-based questionnaire (Lime survey software, version 1.91). We sent MK-2206 datasheet invitations to the selected students on the 18th of March 2013, followed by a reminder one week later. We reviewed the medical files of the university medical service to obtain the documented immunization status of participants. We described mumps cases by time, place

and person. We calculated relative risks (RR) of mumps according to immunization status and a selection of risk factors along with 95% confidence intervals. We considered a p-value <0.05 as statistically significant. We extrapolated the incidence of self-reported parotitis to the complete student population of the KU Leuven. We calculated vaccine effectiveness (VE) as the difference in attack rate between those vaccinated twice and those vaccinated once over the attack rate in those

vaccinated once. We calculated the time in years since the second vaccination based on the documented vaccination data. We analyzed data using STATA 12.00 (STATA Corporation, College Station, TX, USA) and SAS 9.3 (SAS Institute Inc. 2011, Raf inhibitor TX, USA). Informed consent from all students who were included in the study was obtained. On December 14, 2012, the ethics committee of the hospital of KU Leuven approved the study protocol. Between June 16, 2012 and April 16, 2013, 4052 cases were reported from Flanders, of which 1187 were possible, 1294 were probable and 1540 were laboratory-confirmed (overall reported rates: 31.5/100,000 population). Calpain Reported cases of mumps peaked in December 2012 (Fig. 1). Most cases were reported in cities where universities are located, including

Ghent (n = 510), Leuven (n = 419), Kortrijk (n = 415) and Antwerp (n = 365) ( Fig. 2). Fifty-eight percent (n = 2364) of the cases were male and 58% (n = 2348) were between 15 and 25 years of age. Vaccination information was available for 1190 (29%) cases. Of these, 70% (n = 836) were vaccinated twice, 28% (n = 338) were vaccinated once and 2% (n = 16) were unvaccinated. Orchitis was reported in 11% (n = 145) of male cases for whom the status of complications was known. Other complications included meningitis (n = 8; 0.2%) and pancreatitis (n = 5; 0.1%). Between June 16, 2012 and April 16, 2013, 128 specimens were collected from Flanders and tested for mumps virus at the NRC. All specimens were tested by PCR; 53% were confirmed. Genotyping was performed in41 specimens.