The impact of COVID-19 on nurse staffing levels and healthcare- associated infections in medical institutions: A retrospective cohort study

Background: In Korea, various policies had been introduced to improve the nursing shortage problem even before COVID-19, but there is still a shortage of nurses, and it is unclear how this, combined with the impact of infectious diseases, has affected staff nursing grades and healthcare-associated infections(HAIs). This study aimed to evaluate changes in nurse staffing levels in medical institutions in Korea and their impact on HAIs during the COVID-19 pandemic. Methods: A total of 100,417 patients who were admitted to an intensive care unit(ICU) or general ward after a diagnosis or confirmation of COVID-19 from 2020 to 2022 were included in this study. To evaluate the effect of nurses on HAIs, nurse-to-bed(patient) ratio and fixed night shift nurses were considered as nurse factors. A HAI is defined as a patient with a diagnosed or confirmed COVID-19 infection more than seven days after admission or within seven days after discharge. To evaluate the association between nurse staffing levels and HAIs, survival analyses were performed using Cox proportional hazards models, adjusting for covariates. Results: Of the patients admitted to an ICU or general ward, 4.5% and 12.2% had in-hospital COVID-19 infection, respectively. Survival analysis showed that HAIs increased as the number of patients per nurse increased for both general ward and ICU patients. Additionally, compared with medical institutions that do not operate fixed night shift nurses, HAIs increased as the proportion of night nurses increased, but decreased to less than 10%. Conclusions: This study shows that securing nurses and operating an appropriate proportion of night nursing staff is important for infection control within medical institutions. In the event of an infectious disease outbreak, infection prevention activities through appropriate staffing are important, and healthcare-associated infections can be reduced by securing appropriate nurse staffing and maintaining an appropriate proportion of nurses on night shifts.