Quantifying SARS-CoV-2 Infection Risks in Inpatient Psychiatric Settings: A Risk Assessment Model

Background/Objective: In March, 2020, SARS-CoV-2 precipitated a global pandemic. Highly infectious and more likely to cause severe disease in those with underlying comorbidities, the virus necessitated surveillance and risk mitigation strategies. While vaccination efforts have seen relaxing of many of these measures, certain populations, namely the inpatient psychiatric population, remain at-risk for infection and complications. Methods: This retrospective cohort study identified significant demographic, health related, and facility-based predictors of hospital acquired COVID-19 infection. Relevant data was collected from admissions and readmissions at an inpatient psychiatric hospital from June 2020 to June 2022. Univariate Chi-squared and Student’s t-tests were employed to identify significant differences in frequencies of predictors between nosocomial COVID-19 cases and controls; covariates reaching significance were included in a Cox Proportional Hazards model to assess temporal infection risks. A sensitivity analysis was conducted for Cox regression excluding positive SARS-CoV-2 tests ambiguous with respect to nosocomial origin. Results: Of 10,845 admissions, 40 tested positive for SARS-CoV-2 during hospital stay. Patients infected with SARS-CoV-2 were older, (p<0.001), more likely to be discharged from certain units (p<0.001), less likely to be vaccinated (p<0.001), showed higher prevalence of cardiovascular disease (p<0.001) and had longer lengths of stay (p=0.0019). Cox regression identified two discharge units, a general inpatient (HR: 57.2; 95% CI: 5.870, 557.320; p=0.0005) and intensive care unit (HR: 32.4; 95% CI: 3.239, 324.194; p=0.0031), as significantly associated with increased risk of infection. Sensitivity analysis excluding cases of unconfirmed nosocomial origin yielded no significant predictors of SARS-CoV-2 infection risk. Conclusion: In an inpatient psychiatric setting, unit of discharge, cardiovascular disease, age, vaccination status and length of stay were associated with nosocomial SARS-CoV-2 infection risk. These factors are known correlates with diagnosis, severity and duration of psychiatric illness. Thus, risk reduction efforts, especially vaccination, should be targeted to patients with severe mental illness. By assessing predictors of hospital-acquired SARS-CoV-2 infection and identifying areas of focus for interventions in inpatient psychiatric settings, this study adds to important public health literature on the inpatient psychiatric population.