Association of Early Minocycline Use with Secondary Infections in Patients with Severe Fever with Thrombocytopenia Syndrome: A Multicenter Retrospective Cohort Study

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging tick-borne infection disease in which secondary infections may worsen clinical outcomes, particularly in severe cases. This multicenter retrospective cohort study included 1975 laboratory-confirmed SFTS patients from three hospitals in Anhui, China (2011–2025), evaluating whether early minocycline use was associated with lower odds of secondary infections and differences in inflammatory cytokine levels. Propensity score matching was used to balance measured baseline characteristics between the minocycline and control groups. Logistic regression and exploratory subgroup analyses were performed. Among 1975 patients with confirmed SFTS, 548 received minocycline and 1427 did not. The incidence of secondary infection was lower in the minocycline group than in the control group (44.22% vs. 52.99%). Site-specific analysis showed that pulmonary infections were less frequent in the minocycline group (41.83% vs. 49.82%), whereas differences in bloodstream and urinary tract infections were not statistically significant. Multivariate logistic regression showed that early minocycline use was associated with lower odds of secondary infection (OR = 0.62, 95% CI: 0.47–0.82). In an exploratory cytokine analysis, serum interleukin-8 (IL-8) and IL-10 levels were lower in the minocycline group after matching. Early minocycline use was associated with lower odds of secondary infections, particularly pulmonary infections, in patients with SFTS.