GEE results revealed that zone 1 ROP, stage 3 ROP, older baseline PMA, RDS, NEC, and sepsis were associated with increases or decreases in the serum levels of GM-CSF, IL-5, IL-15, ICAM-1, TNF-α, and TNFR-2 in premature infants. This evidence concerns the gene IL15 and necrotizing enterocolitis.