Figure 1

Decreased serum response to the influenza vaccine in the elderly. Sera isolated before (t0) and after vaccination (t7 and t28) were evaluated in HAI. Results are expressed as reciprocal of the titers. Non-parametric analyses were calculated by Mann-Whitney test (two-tailed), using GraphPad Prism 5 software. See text for differences between young and old groups. The numbers of individuals are given in Table 1.