OBJECTIVE To identify the influence factors associated with 28-day fatality among COVID-19 hospitalizations and to analyze the interaction between the disease severity at admission and the use of hospital preparations.METHODS A retrospective review of records from COVID-19 hospitalizations aged 18 to 90 who were admitted to the Jiangsu Province Hospital of Chinese Medi-cine from December 15,2022 to January 15,2023 were conducted.Patients who died or were lost to follow-up within 48 h of admis-sion were excluded.Patients were divided into survival and death groups based on their 28-day fatality status.Descriptive statistics were used to characterize the two groups and multivariate logistic regression models were employed to identify factors influencing 28-day fatality risk.The interaction between the severity of illness at admission and the use of hospital preparations was explored through cross-over analysis and hierarchical regression analysis.RESULTS Significant differences were observed between the survival and death groups in terms of severity of illness at admission,hospital preparations usage,steroid therapy,age,platelet count,lactate dehydro-genase levels,and urea(P<0.05.Crossover analysis and hierarchical logistic regression analysis revealed a significant antagonistic interaction between the severity of illness at admission and the use of hospital formulations both before adjustment(RERI=-20.678,95%CI:-33.703～-7.652;APAI=-2.301,95%CI:-4.027～-0.575 and after adjusting for gender,age,clinical characteristics and further adjusting for laboratory parameters(RERI=-5.972,95%CI:-10.564～-1.380;APAI=-2.205,95%CI:-4.131～-0.279,and it was an antagonistic interaction both before(SI=0.279,95%CI:0.157～0.493 and after adjustment(SI=0.222,95%CI:0.095～0.523.CONCLUSION The use of hospital preparations significantly reduces the 28-day fatality risk among COV-ID-19 hospitalizations and a clear antagonistic interaction was observed between the disease severity at admission and the use of hospi-tal preparations.