Effect of rituximab on T-cell function after vaccinations. IFN-γ–secreting T cells were determined by ELISPOT at 0, 1, 4, and 24 weeks after vaccination with S pneumoniae and Hib vaccines in patients with ITP who received rituximab (n = 17) or placebo (n = 6) 6 months earlier (*P < .05; bars represent SEM).