Nearly 700 4-year U.S. colleges mandated students receive COVID-19 vaccinations in fall 2021. Using data on college policies and county health, we estimate how mandates affect surrounding communities. Event studies from August to November 2021 show that mandates covering all colleges in a county reduced COVID-19 deaths by 5.6 per 100,000 persons, a 4.6% reduction in the U.S. total during this period. Mandates reduced COVID cases by 504 and ICU admissions by 16.2 per 100,000, though we see no statistically significant impact on hospitalizations. Impacts are larger in counties with larger college populations and low estimated ex-ante student vaccination rates.