The University of California (UC) system will require all eligible students and staff to show proof of receiving a COVID-19 booster shot in the coming semester.

The decision will affect UCLA, UC Irvine, UC San Diego, UC Riverside, UC Berkeley, UC Davis, UC Merced, Riverside, UC San Francisco, UC Santa Barbara, and UC Santa Cruz.

“Under existing UC policy, students, faculty, and staff are required to keep their vaccination status up to date,” University of California President Michael V. Drake said in a letter Tuesday. “The policy mandates COVID-19 boosters for those who are eligible.”

With the Omicron variant of COVID-19 becoming the dominant variant in the U.S. and positive cases gradually increasing in L.A. County, UCLA announced that it would reinstate online courses for the 2022 winter quarter, which begins January 3.

The university joins at least six other UCs such as Irvine and Santa Cruz in implementing online winter courses in lieu of on-campus classes.

The plan for UCLA will be to hold classes remotely for the first two weeks of the quarter and have students return to campus on January 18. By that time, students will have to show proof of receiving a booster, as all students were already required to be fully vaccinated in the previous semester.

UCLA also announced that students and faculty returning to campus in January would go through a “robust” COVID-19 testing system.

UC Irvine said that it will, too, implement a testing regimen before returning to in-person instruction, with Chancellor Howard Gillman not committing to a return date, instead saying testing results after the holidays would be an indicator.

“This will allow for at least one cycle of testing, sequestration, and re-testing for appropriate members of our community, especially our returning residential students, and continues the testing requirements and opportunities we practiced throughout the fall quarter,” Gillman said in an update. “The result of these testing protocols will give us the information necessary to decide how quickly we can return to in-person instruction. We are currently working through the related logistics, so stay tuned for specific details in the days ahead.”