Antibody response to vaccinations. IgG specific antibodies to (A) S pneumoniae and (B) Hib detected in the first month after the pneumococcal polysaccharide vaccine and the conjugate Hib vaccine. Patients had ITP and had been treated with rituximab (n = 14) or placebo (n = 6) 6 months before vaccinations. Vaccine responders were defined as patients who achieved at least a fourfold increase in antibody titer compared with baseline values.