A big study in China looked at people with COVID‑19 who got the peptide thymosin‑alpha‑1 and found they did worse than those who didn’t get it. They were more likely to stay sick, die, need a ventilator, develop lung injury, kidney injury, and spend longer in the ICU. Starting the peptide later or using it in very sick patients made the risk even higher.

Thymosin alpha 1 (T&#x3b1;1) is widely used to treat patients with COVID-19 in China; however, its efficacy remains unclear. This study aimed to explore the efficacy of T&#x3b1;1 as a COVID-19 therapy. We performed a multicenter cohort study in five tertiary hospitals in the Hubei province of China between December 2019 and March 2020. The patient non-recovery rate was used as the primary outcome. All crude outcomes, including non-recovery rate (65/306 <i>vs.</i> 290/1,976, <i>p</i> = 0.003), in-hospital mortality rate (62/306 <i>vs.</i> 271/1,976, <i>p</i> = 0.003), intubation rate (31/306 <i>vs.</i> 106/1,976, <i>p</i> = 0.001), acute respiratory distress syndrome (ARDS) incidence (104/306 <i>vs.</i> 499/1,976, <i>p</i> = 0.001), acute kidney injury (AKI) incidence (26/306 <i>vs.</i> 66/1,976, <i>p</i> &lt; 0.001), and length of intensive care unit (ICU) stay (14.9 &#xb1; 12.7 <i>vs.</i> 8.7 &#xb1; 8.2 days, <i>p</i> &lt; 0.001), were significantly higher in the T&#x3b1;1 treatment group. After adjusting for confounding factors, T&#x3b1;1 use was found to be significantly associated with a higher non-recovery rate than non-T&#x3b1;1 use (OR 1.5, 95% CI 1.1-2.1, <i>p</i> = 0.028). An increased risk of non-recovery rate associated with T&#x3b1;1 use was observed in the patient subgroups with maximum sequential organ failure assessment (SOFA) scores &#x2265;2 (OR 2.0, 95%CI 1.4-2.9, <i>p</i> = 0.024), a record of ICU admission (OR 5.4, 95%CI 2.1-14.0, <i>p</i> &lt; 0.001), and lower PaO2/FiO2 values (OR 1.9, 95%CI 1.1-3.4, <i>p</i> = 0.046). Furthermore, later initiation of T&#x3b1;1 use was associated with a higher non-recovery rate. T&#x3b1;1 use in COVID-19 patients was associated with an increased non-recovery rate, especially in those with greater disease severity.