Direct medical costs of respiratory infections in adults: A multicenter retrospective analysis in Thai Nguyen, Vietnam

Background: Respiratory infections remain a significant health and economic burden in low- and middle-income countries, including Vietnam. This study aimed to estimate the direct medical costs of respiratory infections among adults in Thai Nguyen, Vietnam and identify some influencing factors. Methods: In this retrospective study, we analyzed direct medical costs of inpatient aged ≥18 discharged with respiratory infections (ICD-10 codes: J00 – J22) in seven hospitals in Thai Nguyen, Vietnam. Records of patients admitted between 11 November 2022 and 30 June 2025 were included. A generalized gamma linear mixed model with log-link function was used to identify influencing factors, including patient demographics and infection-related characteristics. All costs are expressed in US$, adjusted to 2025 levels. Results: The analysis included 25,081 inpatients with 28,016 respiratory infection episodes. Most were female (54.3%), Kinh ethnicity (70.0%), and aged ≥60 (58.1%). Pneumonia (J18) was the most common primary diagnosis (58.5%), followed by bacterial pneumonia (J15, 18.7%). Common secondary diagnoses included hypertension (27.1%), gastro-oesophageal reflux disease (7.8%), and type 2 diabetes (6.9%). The median total medical cost per inpatient episode was US$174.9 (IQR 104.7–243.3), mainly driven by hospital bed days (median US$83.5), followed by medicine costs (US$52.7), and laboratory tests (US$12.7). Pneumonia was the most expensive disease, with median costs of US$218.8 (J15), US$1,179.4 (J16), and US$181.5 (J18). Primary diagnosis, age, gender, hospital level, length of stay, and additional secondary diagnosis were associated with higher direct medical costs. Conclusion: Hospitalized adults with respiratory infections incurred a median direct medical cost of US$174.9 in Thai Nguyen, Vietnam. Costs were substantially higher for lower respiratory tract infections and were influenced by hospital level, length of stay, and comorbidities. These findings highlight the need for preventive measures and efficient hospital resource allocation in Vietnam.