Risk categorization and outcomes among healthcare workers exposed to COVID-19: A cohort study from a Thai tertiary-care center

BACKGROUND: A risk categorization tool for healthcare workers (HCWs) exposed to COVID-19 is crucial for preventing COVID-19 transmission and requires validation and modification according to local context. METHODS: From January to December 2021, a prospective cohort study was conducted among Thai HCWs to evaluate the performance of the specifically-created risk categorization tool, which classified HCWs into low-risk (LR), intermediate-risk (IR), and high-risk (HR) groups based on types of activities, duration of exposure, and protective methods used during exposure. Subsequent measures were determined for the HCWs based on the risk categories. RESULTS: 1891 HCWs were included; 52%, 25% and 23% were LR, IR, and HR, respectively. COVID-19 was diagnosed in 1.3%, 5.1% and 27.3% of LR, IR and HR HCWs, respectively (P <0.001). Independent factors associated with COVID-19 were household or community exposure [adjusted odds ratio (aOR), 1588.68; P <0.001), being HR (aOR, 11.94; P <0.001), working at outpatient departments (aOR, 2.54; P <0.001), and no history of COVID-19 vaccination (aOR, 2.05; P = 0.01). The monthly rates of COVID-19 among LR, IR, and HR HCWs significantly decreased after the incremental rate of full vaccination. In-hospital transmission between HCWs occurred in 8% and was mainly due to eating at the same table. CONCLUSION: The study risk categorization tool can differentiate risks of COVID-19 among the HCWs. Prevention of COVID-19 should be focused on HCWs with the identified risk factors and behaviors associated with COVID-19 development and encouraging receipt of full vaccination.