IFNG and infection: Randomly sampled participants demonstrated no significant differences in the levels of cytokine-producing T-cells measured by ELISpot compared with their parental cohorts, indicating that they are representative of their respective cohorts (sampled IFNγ SI 9.4 ± 1.1 versus parental 11.8 ± 1.4 after vaccination, and sampled IFNγ SI 14.6 ± 3.0 versus parental 13.5 ± 1.7 after infection).