Pneumococcal immunization in immunocompromised hosts: where do we stand?

Immunocompromised patients are all at risk of invasive pneumococcal disease, of different degrees and timings. However, considerable progress in pneumococcal immunization over the last 30 years should benefit these patients. The 23-valent polysaccharide vaccine has been widely evaluated in these populations, but due to its low immunogenicity, its efficacy is sub-optimal, or even low. The principle of the conjugate vaccine is that, through the protein conjugation with the polysaccharide, the vaccine becomes more immunogenic, T-cell dependent, and thus providing a better early response and a boost effect. The 7-valent conjugate vaccine has been the first one to be evaluated in different immunocompromised populations. We review here the efficacy and safety of the different antipneumococcal vaccines in cancer, transplant and HIV-positive patients and propose a critical appraisal of the current guidelines.