Although there was a significant correlation between IFN-γ+ T cell response and N-binding IgG level in unvaccinated donors (P = 0.0044; Supplementary Fig. 7), N-binding IgG responses waned at a greater rate in vaccinated versus unvaccinated donors, whereas IFN-γ+ T cell responses were maintained regardless of vaccination status, albeit number of donors beyond 50 weeks post-infection were low (Supplementary Fig. 8). This evidence concerns the gene IFNG and infection.