CD27 and idiopathic pulmonary fibrosis: The prevalence of CD27+ Tc cells was heightened in IPF when compared to healthy subjects only before vaccination (2.64% vs 0.61%; p=0.002 before vaccination; 0.31% vs 0.20%; p=0.43 after the 1st dose; 0.26% vs 0.14%; p=0.13 after the 2nd dose).