Long-term outcomes of mesenchymal stem cell therapy in severe COVID-19 patients: 3-year follow-up of a randomized, double-blind, placebo-controlled trial

• MSC therapy demonstrates long-term safety in severe COVID-19 patients over a 3-year follow-up, with no significant increase in new-onset complications or tumor marker levels. • Patients receiving MSCs showed a higher rate of normal CT findings (46.94% vs 34.48%) and improved general health scores on SF-36 (67.0 vs 50.0), suggesting potential benefits for lung recovery and quality of life. • No significant differences were observed in total lung severity scores, 6-minute walking distance, pulmonary function tests, or Long COVID symptoms between MSC and placebo groups. • The study supports the potential of MSC therapy as a safe adjunct treatment for severe COVID-19, with possible advantages in lung recovery and quality of life for Long COVID patients.