<p>Supplementary material 1.</p>

Annual rehospitalization rates were calculated per 100 person-years. The analysis included demographics, hospital discharge disposition, and vaccination-related variables. Cox proportional hazards models with deaths considered as competing risks were used.

Of the 59,001 individuals included, 1,957 (3.3%) experienced rehospitalization. The main finding was that a complete vaccination regimen with a booster (≥3 doses) was associated with a 39% reduction in the risk of rehospitalization (sHR: 0.61; 95% CI: 0.52–0.73), while older age, multimorbidity, and Black race/skin color emerged as significant risk factors. Full vaccination with booster doses offered protection against COVID-19-related rehospitalization; however, racial inequities, advanced age, and comorbidities remain important risk factors.

Public health policies that expand periodic booster vaccination, strengthen health education, and address social vulnerabilities are urgently needed as a fundamental strategy for preventing future pandemics.</p></div>