These stats are based on averages and so don’t necessarily apply in the individual case, but it’s still helpful to post them for some perspective. Right now, a 15-24 year old is slightly more likely to die from flu than from Covid. Those probabilities will correlate with relative risk of hospitalization and withdraw from school. Now, the flu has a vaccine which is usually available prior to the start of the UC academic year. Covid doesn’t yet have a widely available vaccine. Another strike against is that it might be more contagious than flu for all we know. Offsetting these factors is that the university is being very vigilant, as @Mom2Melcs has pointed out, and that makes sense given the news coverage and lack of vaccine.