Invasive pneumococcal disease

Invasive pneumococcal disease is disease caused by Streptococcus pneumoniae after the organism moves beyond its usual asymptomatic colonization of the respiratory tract, sinuses, or nasal cavity to cause pathogenic infection in susceptible individuals ^[1]. It includes severe manifestations such as pneumonia, meningitis, and sepsis, as well as other invasive infections described for pneumococcus ^[1][2].

Pneumococcal pneumonia can cause fever, chills, coughing, rapid or labored breathing, and chest pain ^[1]. In older adults, pneumonia may be preceded by tachypnea and nonspecific signs such as rapid shallow breathing, sleep disturbance, chest pain, and decreased appetite ^[1]. Invasive pneumococcal disease can also manifest as meningitis, sepsis, osteomyelitis, septic arthritis, endocarditis, peritonitis, pericarditis, cellulitis, or brain abscess ^[1].

The use of polysaccharide-protein conjugate vaccines has been pivotal in reducing the incidence of invasive pneumococcal disease, although non-vaccine serotypes have emerged ^[3]. Multivalent pneumococcal vaccines addressing increasing numbers of Streptococcus pneumoniae types have been licensed over the last 22 years ^[3]. Streptococcus pneumoniae type 3 remains a major cause of invasive pneumococcal disease in several countries ^[3].

Streptococcus pneumoniae typically colonizes the upper respiratory tract, sinuses, and nasal cavity of healthy carriers without causing symptoms, and transmission occurs by direct person-to-person contact via respiratory droplets as well as by autoinoculation in persons carrying the bacteria in their upper respiratory tract ^[1]. When host defenses are impaired, colonizing pneumococci can translocate from the nasopharynx to normally sterile sites, producing invasive pneumococcal disease ^[1].

Routine childhood pneumococcal vaccination is recommended by the World Health Organization and is included in immunization schedules in several countries ^[1]. Multivalent pneumococcal conjugate vaccines have been pivotal in reducing invasive pneumococcal disease incidence, despite emergence of non-vaccine serotypes ^[3]. In childhood vaccination programmes, pneumococcal conjugate vaccine introduction has led to a notable decrease of severe invasive pneumococcal disease in vaccinated children, although non-vaccine types have concurrently increased and caused invasive disease in unvaccinated populations such as older adults ^[2]. In adults, PCV13 and PPSV23 have demonstrated efficacy or effectiveness against vaccine-type invasive pneumococcal disease and pneumococcal pneumonia, and PCV15 and PCV20 have been licensed for adult use based on safety and immunogenicity ^[4]. Emerging antibiotic resistance and serotype replacement continue to motivate vaccine improvement and new prevention strategies ^[3][2].

1. 1 Wikipedia contributors. Streptococcus pneumoniae - Wikipedia [Internet]. Wikipedia. cited 3 Sept 2026. Available from: https://en.wikipedia.org/wiki/Streptococcus_pneumoniae
2. 2 Narciso AR et al. Streptococcus pneumoniae epidemiology, pathogenesis and control. Nat Rev Microbiol. 2025 Apr. PMID: 39506137. doi: 10.1038/s41579-024-01116-z. PubMed: https://pubmed.ncbi.nlm.nih.gov/39506137/
3. 3 Micoli F et al. Strengths and weaknesses of pneumococcal conjugate vaccines. Glycoconj J. 2023 Apr. PMID: 36652051. doi: 10.1007/s10719-023-10100-3. PubMed: https://pubmed.ncbi.nlm.nih.gov/36652051/
4. 4 Farrar JL et al. Systematic Review and Meta-Analysis of the Efficacy and Effectiveness of Pneumococcal Vaccines in Adults. Pathogens. 2023 May 19. PMID: 37242402. doi: 10.3390/pathogens12050732. PubMed: https://pubmed.ncbi.nlm.nih.gov/37242402/