As most PBMC from PASC patients expressed IDO2, we next analyzed 500,000 PBMC from 9 PASC patients and 14 fully recovered patients from the MUSCLE-PASC study by metabolomics for 219 metabolites covering most of the central carbon metabolic pathways, including glycolysis, TCA cycle, amino acids, pentose phosphate pathway, and NAD metabolism.16 Here, IDO2 is linked to long COVID-19.