This report describes a 12-year-old girl who developed vaccine-type pneumococcal septicemia (type 4, Danish nomenclature) 2 years after splenectomy for recurrent idiopathic thrombocytopenia despite vaccination with the 23-valent vaccine 4 weeks before surgery and antibiotic prophylaxis with penicillin V. The disease presented as high fever with shivering and vomiting followed by disseminated petechiae and a deteriorated general condition. Initial laboratory studies showed severe sepsis with leucocytopenia and thrombocytopenia, a markedly elevated CRP, and disseminated intravascular coagulation. Despite antibiotic treatment, which was initiated with clindamycin, cefotaxime and trimethoprim/sulfamethoxazole and was switched to cefotaxime and penicillin after the result of the blood culture had been obtained, the patient had to be ventilated, and hemofiltration became necessary because of acute renal insufficiency. Furthermore, she required amputation of all her toes because of severe necrosis. No type-specific pneumococcal antibody titers were detected during and after infection. It remains unclear whether the susceptibility to Streptococcus pneumoniae was due to primary failure of antibody production or a decline in antibody levels after vaccination. Patients and/or their relatives should be informed that neither vaccination nor continuous antibiotic prophylaxis can guarantee full protection against infection with S. pneumoniae in patients after splenectomy.