Community-acquired pneumonia: paving the way towards new vaccination concepts

Despite the availability of antimicrobial agents and vaccines, community-acquired pneumonia remains a serious problem. Severe forms tend to occur in very young children and among the elderly, since their immune competence is eroded by immaturity and immune senescence, respectively. The main etiologic agents differ according to patient age and geographic area. Streptococcus pneumoniae, Haemophilus influenzae, respiratory syncytial virus (RSV) and parainfluenza virus type 3 (PIV-3) are the most important pathogens in children, whereas influenza viruses are the leading cause of fatal pneumonia in the elderly. Effective vaccines are available against some of these organisms. However, there are still many agents against which vaccines are not available or the existent ones are suboptimal. To tackle this problem, empiric approaches are now being systematically replaced by rational vaccine design. This is facilitated by the growing knowledge in the fields of immunology, microbial pathogenesis and host response to infection, as well as by the availability of sophisticated strategies for antigen selection, potent immune modulators and efficient antigen delivery systems. Thus, a new generation of vaccines with improved safety and efficacy profiles compared to old and new agents is emerging. In this chapter, an overview is provided about currently available and new vaccination concepts.