All University of Arkansas students are being required to have up-to-date vaccinations in order to attend classes following a mumps outbreak on campus.

The state Department of Health on Friday issued a notice telling students they need to be immunized with at least two doses of the mumps vaccine or sit out of class for 26 days. The agency says nine cases of the viral disease have been diagnosed at the Fayetteville school this fall and other possible cases are being investigated.

University spokesman Zac Brown says the school has vaccination records for its roughly 27,000 students and has already contacted the 407 who don’t have current vaccinations.

Brown says the university anticipates many of those students will come to a health center to be inoculated Monday.