Vaccinations are safe and effective in immunocompromised patients. Apparently most vaccines in this patient population are underutilized. General vaccination recommendations are expressed for influenza, diphtheria and tetanus. Pneumococcal, meningococcal und Haemophilus influenzae B immunizations are specially indicated for patients with or developing B-cell-deficiency. Live attenuated vaccines are usually contraindicated. The efficacy of the immunization and its indication can be additionally measured by antibody response, which is usually decreased compared to healthy subjects. Immunocompromised hosts with cancer will benefit from consistent immunization practices. Further clinical trials are urgently warranted.