CD4 and HIV infectious disease: To minimize the influence of duration of HIV infection, a prospective observational cohort of adult patients with primary HIV infection (seroconversion window ≤6 months) has shown that HBV coinfection (adjusted hazards ratio 3.46; 95 % CI 1.16–10.32) was an independent predictor of immunological progression that was defined as the occurrence of a CD4 cell count <350 cells/μl 3 months or more after diagnosis of primary HIV infection [400].