Figure 1.

Effects of inflammation on interleukin-6 and fatigue. (A) Change in circulating interleukin-6 before and after vaccine (V base and V 4 Hrs) and placebo injection (P base and P 4 Hrs). Typhoid vaccination evoked a robust inflammatory response with an approximately threefold increase in plasma interleukin-6 from mean (± SE) 1.29 ± .38 pmol/L at baseline to 3.74 ± .27 pmol/L at 4 hours [t₁₉ = 5.93, p < .001]. The placebo condition was not associated with any change in interleukin-6 from .97 ± .23 pmol/L at baseline to .90 ± .18 pmol/L at 4 hours [t₁₉ = −.54, p = .59]. (B) Change in fatigue before and after typhoid vaccination and placebo saline injection. Typhoid vaccination, but not placebo injection, was associated with a significant increase in fatigue as shown by mean (± SE) fatigue visual analog scale 16.18 ± 12.57 at baseline to 42.40 ± 22.52 at 4 hours [t₁₉ = 6.05, p < .001] for typhoid vaccination and 22.08 ± 17.72 at baseline to 29.60 ± 17.94 at 4 hours [t₁₉ = 1.93, p = .07] for placebo injection. IL-6, interleukin-6; n.s., p = non significant; VAS, visual analog scale.