Study subjects
Two hundred sixty-five HCWs were selected for the evaluation of IFN-γ producing T-cells by an Enzyme Linked Immuno-Spot (ELISpot) assay in response to nine HCV genotype 4a overlapping 15mer peptide pools covering the whole viral genome. The study protocol was approved by the NLI-Institutional Review Board (IRB), and all subjects gave informed consent prior to enrolment. The demographic characteristics of the participants were previously reported [14].