Statistical analysis
Statistical analysis was performed using GraphPad Prism software, version 6 (GraphPad; La Jolla, CA, USA). The Mann–Whitney U test was used for parameter comparison between two subject groups. The frequencies of epitope-specific CD8+ T cells are presented as median with 95% confidence interval (CI95%) or median with range.P -Value (two-tailed) below 0.05 (P ≤ 0.05) was considered to be statistically significant.