The percentages of Th1/17 Tregs subpopulation within CD4+ cells were significantly lower in IPF patients, than in healthy volunteers before vaccination (1.39% vs 2.20%; p<0.000), but not after the vaccine administration (2.36% vs 2.59%; p=0.83; and 2.90% vs 2.21%; p=0.20). Here, CD4 is linked to idiopathic pulmonary fibrosis.