SARS-CoV-2 breakthrough infections in a retrospective cohort of vaccinated university students and employees.

Breakthrough SARS-CoV-2 infections, despite widespread vaccination efforts, remain a critical concern in densely populated environments such as universities, where transmission dynamics are influenced by close contact and shared facilities. In this retrospective cohort study conducted at the University of Miami from December 2020 through October 2021, we analyzed infection rates among 38,783 students (61%) and employees (39%) to evaluate vaccine effectiveness and the necessity of ongoing surveillance. Our findings revealed that vaccinated individuals had a lower infection rate (1.8%) compared to their unvaccinated counterparts (2.6%), with students exhibiting fewer breakthrough infections (1.5%) than employees (5.6%). Notably, the median duration from full vaccination to breakthrough infection was shorter in students, suggesting potential differences in exposure risk or immune response. These results highlight the protective impact of vaccines in this population while emphasizing the importance of tailored public health strategies, particularly in institutional settings where behavioral and occupational differences contribute to infection disparities. Continuous monitoring remains essential to refine mitigation efforts and enhance pandemic preparedness.