Effectiveness of pneumococcal vaccines in preventing pneumonia in adults, a systematic review and meta-analyses of observational studies

S. pneumoniae can cause a wide spectrum of diseases, including invasive pneumococcal disease and pneumonia. Two types of pneumococcal vaccines are indicated for use in adults: 23-valent pneumococcal polysaccharide vaccines (PPV23) and a 13-valent pneumococcal conjugate vaccine (PCV13). This study reviews the literature assessing pneumococcal vaccine effectiveness  against community-acquired pneumonia in adults among the general population, the immunocompromised and subjects with underlying risk factors in real-world settings.