Early antiviral use and supplemental oxygen decrease the risk of secondary bacterial infections: a multi-centre, nested, case-control study.

Background: The purpose of this study was to evaluate the treatment strategies that dictate the host susceptibility to secondary bacterial infections during coronavirus disease 2019 (COVID-19).

Methods: This nested, case-control study was conducted in three general hospitals in China between 1 December 2022 and 1 March 2023. A total of 456 confirmed COVID-19 patients matched 1:2 (152 cases and 304 controls) based on age, sex, disease severity and age-adjusted Charlson Comorbidity Index (aCCI) using propensity-score matching (PSM) were included. Association of secondary bacterial infections with treatment strategies including the supportive measures, antiviral, and antibacterial therapies were the main outcome measures.

Findings: Conditional logistic regression analyses demonstrated that among categorical variables, use of antibiotics, antivirals, intravenous injection of human immunoglobulin, glucocorticoids or anticoagulants were not associated with the risk of secondary bacterial infections in the COVID-19 patients. The use of supplemental oxygen by either low (odds ratio (OR): 0.18, P<0.001) or high flow (OR: 0.06, P<0.001), but not through ventilators were associated with significant protection against secondary bacterial infection. In contrast, feeding through gastric tube (OR: 10.97, P<0.001) or parenteral nutrition (OR: 3.97, P=0.002) was associated with significant increase in the risk of secondary bacterial infections. Similar data were obtained when data were analysed using continuous variables. Further, the early (<5 days post symptom onset, OR: 0.09, P<0.001), but not the late use of antivirals was associated with protection against secondary bacterial infections.

Conclusions: Oxygen supplementation in non-ventilator settings and early use of antivirals were associated with decreased incidences of secondary bacterial infections, while parenteral nutrition or tube feedings were associated with increased incidences of secondary bacterial infections.