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Date of preparation: March 2018

What is invasive pneumococcal disease (IPD)?  

IPD is a serious illness caused by Streptococcus pneumoniae.1 IPD is commonly defined as morbidity associated with the isolation of pneumococci from a normally sterile body site, such as the blood stream, or sites secondary to blood stream spread, e.g. meningitis or septic arthritis. 2

Over 90 serotypes of Streptococcus pneumoniae have been identified. 2 Prior to the introduction of pneumococcal conjugate vaccines, 6–11 serotypes accounted for 70% of all IPD occurring in children worldwide. 3

Types of invasive pneumococcal diseases (IPDs)  

  • Pneumococcal meningitis
    Pneumococcal meningitis is a serious disease in which the meninges (the membranes that surround and protect the brain and spinal cord) become inflamed . 4 Streptococcus pneumoniae causes between 13% and 19% of cases of bacterial meningitis and an estimated 3000–6,000 cases per year occur in the USA alone. 5
  • Pneumococcal bacteraemia
    Bacteraemia without a known site of infection is a common invasive clinical presentation of pneumococcal infection among children younger than 5 years of age, accounting for approximately 538,000 cases in this age group (in the year 2000), with varying incidence depending on the geographic setting. 56 The incidence of bacteraemia without focus is likely to be underestimated in many settings where blood cultures are not routinely obtained from febrile children. 6 Bacteraemia occurs in 25–30% of patients with pneumococcal pneumonia and the overall case fatality rate is around 20% and can be as high as 60% in elderly patients. 5 Bacteraemic pneumonia accounts for 12–16% of all IPD in children 2 years of age and younger. 5

Types of non-invasive pneumococcal diseases

Besides invasive diseases, pneumococcus can also cause non-invasive diseases, such as pneumonia (without bacteraemia) or acute otitis media (AOM). 5 The aetiology of these non-invasive diseases, particularly pneumonia often remains unestablished. Despite an increase in understanding of causative pathogens and pathogenic mechanisms and the development of new drugs initial treatment is still often empiric, because in as many as 50% of cases, a responsible pathogen is not found. 7

Otitis media is a generic term used to describe the inflammation around the middle ear, without referral to aetiology or pathogenesis. 8

  • Bacterial pneumonia
    Pneumonia is usually caused by bacteria or viruses 9 and Streptococcus pneumoniae is thought to be responsible for 30–50% of bacterial pneumonia cases. 10 Pneumonia primarily affects very young infants and the elderly 11 and Streptococcus pneumoniae is the most common cause of bacterial pneumonia amongst children in the developing world. 12 Bacterial pneumonia also accounts for 12–16% of IPD among children 2 years of age or under in the USA. Therefore, the public health burden of the disease is significant. 5 The economic costs of pneumonia can also impact negatively on healthcare systems and productivity. 13
  • Acute otitis media (AOM)
    AOM occurs when a bacterial or viral infection causes mucus to build up in the middle ear and becomes infected. 1415 By 12 months of age, more than 60% of children have had at least one episode of AOM. 5
    Bacterial infection is responsible for up to 92% (50-92%) of AOM cases and 30–49% are caused by pneumococci; 16 the second most common cause is non-typeable Haemophilus influenzae. 16 AOM can also arise as a complication of influenza, measles or pertussis. 17
    AOM is the most common childhood illness for which medical attention is sought, with over 750 million cases every year in children under 5 years of age. 18
    Among parents with children previously diagnosed with AOM, 73% of those who were surveyed had to miss work or rearrange their working hours, resulting in a significant economic burden. 19 The burden on healthcare is also substantial, with an estimated 20 million paediatric office visits annually in the USA. 5


  1. Public Health England. Pneumococcal disease. Available at: [Last accessed June 2015].
  2. WHO. Pneumococcal vaccines WHO position paper – 2012. Weekly epidemiological record 2012; 87:129-44. Available at: [Last accessed January 2015].
  3. Johnson HL, et al. Systematic evaluation of serotypes causing invasive pneumococcal disease among children under five: the pneumococcal global serotype project. PLoS Med 2010; 7: pii: e1000348.
  4. Meningitis Research Foundation. Pneumococcal meningitis. Available at: [last accessed June 2015]
  5. CDC. Chapter 16: Pneumococcal Disease. In: Atkinson W, Wolfe S, Hamborsky J, eds. Epidemiology and Prevention of Vaccine-Preventable Diseases [Pink Book]. 12th edn. Washington, DC: Public Health Foundation; 2012e: 233–48.
  6. O’Brien KL, et al. Burden of disease caused by Streptococcus pneumoniae in children younger than 5 years: global estimates. Lancet 2009; 374: 893–902
  7. Mandell LA, et al. Community-Acquired Pneumonia* Etiology, Epidemiology, and Treatment. Chest 1995; 109: 35S – 42S.
  8. Medscape. Otitis Media with Effusion. Available at: [last accessed June 2015]
  9. WHO Pneumonia Fact Sheet No 331 November 2014 Available at: [Last accessed June 2015].
  10. Rudan I, et al. Epidemiology and etiology of childhood pneumonia. Bull World Health Organ 2008; 86: 408–16.
  11. National Heart Lung and Blood Institute. Who is at risk for Pneumonia? Available at: [Last accessed June 2015].
  12. UNICEF/WHO, Pneumonia: the forgotten killer of children, 2006.
  13. Sinha A, et al. Cost effectiveness of pneumococcal conjugate vaccination in prevention of child mortality: an international economic analysis. Lancet 2007; 369: 389–96.
  14. Cripps A, et al. Bacterial otitis media: a vaccine preventable disease? Vaccine 2005; 23: 2304–10.
  15. National Institute on Deafness and Other Communication Disorders. NIDCD Fact sheet. Ear infections in children. Available at: [Last accessed Nov 2019] .
  16. Ruohola A, et al. Microbiology of acute otitis media in children with tympanostomy tubes: prevalences of bacteria and viruses. Clin Infect Dis 2006; 43: 1417–22.
  17. Department of Health. Chapter 25: Pneumococcal. In: Salisbury DS, Ramsey M, Noakes, eds. Immunisation against infectious disease [Green book]. London; The Stationary Office; 2006: 295–313.
  18. Monasta L, et al. Burden of Disease Caused by Otitis Media: Systematic Review and Global Estimates. PLoS One 2012; 7: e36226.
  19. Barber C, et al. Acute otitis media in young children – what do parents say? Int J Pediatr Otorhinolaryngol. 2014; 78: 300-6.