g logo nhs blue


This section is part 1 of the PHE pneumococcal guideline summary.

Contents included this summary

Contents not included in this summary

History and epidemiology of the disease



Pneumococcal disease is the term used to describe infections caused by the bacterium Streptococcus pneumoniae (also called pneumococcus).

S. pneumoniae is an encapsulated Gram-positive coccus. The capsule is the most important virulence factor of S. pneumoniae; pneumococci that lack the capsule are normally not virulent. Over 90 different capsular types have been characterised. Prior to the routine conjugate vaccination, around 69% of invasive pneumococcal infections were caused by the ten (14, 9V, 1, 8, 23F, 4, 3, 6B, 19F, 7F) most prevalent serotypes.

Some serotypes of the pneumococcus may be carried in the nasopharynx without symptoms, with disease occurring in a small proportion of infected individuals. Other serotypes are rarely identified in the nasopharynx but are associated with invasive disease. The incubation period for pneumococcal disease is not clearly defined but it may be as short as one to three days.

The organism may spread locally into the sinuses or middle ear cavity, causing sinusitis or otitis media. It may also affect the lungs to cause pneumonia, or cause systemic (invasive) infections including bacteraemic pneumonia, bacteraemia and meningitis.

Transmission is by aerosol, droplets or direct contact with respiratory secretions of someone carrying the organism. Transmission usually requires either frequent or prolonged close contact. There is a seasonal variation in pneumococcal disease, with peak levels in the winter months.

Invasive pneumococcal disease is a major cause of morbidity and mortality. It particularly affects the very young, the elderly, those with an absent or non-functioning spleen and those with other causes of impaired immunity. Recurrent infections may occur in association with skull defects, cerebrospinal fluid (CSF) leaks, cochlear implants or fractures of the skull.

Did you find this guideline summary useful?

full guideline available from…


Public Health England. Pneumococcal: the green book, chapter 25. January 2018.

Contains public sector information licensed under the Open Government Licence v3.0.

First included: May 2019.