CD4 and myeloproliferative disorder: Using an intracellular cytokine assay for IFNγ, TNFα and IL2, Harrington, et al. reported polyfunctional CD8+- and CD4+-T-cells of 35% and 75%, respectively, in 21 patients with BCR-ABL1-negative myeloproliferative neoplasms (MPN) after a median of 21 days after a single dose of BNT162b2 vaccine [15].