Positives

• Patients hospitalized with COVID-19 pneumonia who received tofacitinib had a lower 28-day risk of death or respiratory failure compared with placebo, suggesting an immunomodulatory benefit in inflammatory phases Nejm.
  
  
• A meta-analysis of tofacitinib in COVID-19 found reduced mortality and decreased need for invasive mechanical ventilation without an elevated rate of adverse drug reactions ScienceDirect.
  
  

Negatives

• Mast cell activation symptoms are highly prevalent in Long COVID and overlap with MCAS, but published evidence specifically supporting tofacitinib for MCAS-predominant Long COVID is absent in current literature PMC.
  
  

Hurdles & Side Effects

• Tofacitinib (Xeljanz) carries an FDA boxed warning for serious infections, thrombosis, and cardiovascular events, which makes rheumatologists cautious about off-label prescribing for post-viral indications PubMed.