In the 24 EU/EEA countries reporting data on CD4 cell count at diagnosis among 18,103 persons >15 years-old diagnosed in 2015, nearly half (n=8,490; 47%) of all cases had a CD4 cell count of less than 350 cells/mm3, while 28% (n=5,094) had advanced HIV infection (CD4 < 200 cells/mm3). Here, CD4 is linked to HIV infectious disease.