Pneumococcal disease is a leading cause of serious illness in children and adults. It is caused by a common bacterium, Streptococcus pneumoniae (also known as pneumococcus), which can target different parts of the body to cause non-invasive diseases such as pneumonia, otitis media and sinusitis, as well as invasive pneumococcal disease (IPD), including bacteraemia and meningitis.
Pneumococcal disease particularly affects the very young, the elderly, those with an absent or nonfunctioning spleen and those with other causes of impaired immunity.
Recurrent infections may occur in association with skull defects, cerebrospinal fluid leaks, cochlear implants or fractures of the skull.
How pneumococcal disease spreads
Pneumococcal disease is spread by the bacterial pathogen Streptococcus pneumoniae, an encapsulated Gram-positive coccus. The capsule is the most important virulence factor of Streptococcus pneumoniae; pneumococci that lack the capsule are normally not virulent.
Pneumococcal disease tends to be more common during winter and when influenza and other respiratory viruses are circulating. Sometimes the consequences can be very serious, resulting in systemic infections such as bacteraemic pneumonia, bacteraemia or meningitis.
Between 22-42% of adults with community acquired pneumonia (CAP) in the UK are admitted to hospital This places a burden on limited resources in the NHS. In recent year (1997-98 vs 2004-05) there was a 34% increase in hospital admissions for CAP in England. The most common cause of pneumonia in the UK is Streptococcus pneumoniae.
Disease transmission can occur by aerosol, droplets or direct contact with respiratory secretions of someone carrying the organism. The organism then may spread into the sinuses or middle ear cavity (causing sinusitis or otitis media), lungs (causing pneumonia) or invasive infections (bacteraemic pneumonia, bacteraemia and meningitis). Transmission usually requires either frequent or prolonged close contact.
Did you know?
Before the introduction of routine vaccination, pneumococcal infection killed 43 children per year in England and Wales.
There are two manifestations of pneumococcal disease:
- Non-invasive disease includes lower respiratory tract infections (LRTIs) such as pneumonia and upper respiratory tract infections (URTIs) including sinusitis
- Invasive pneumococcal disease occurs when the pneumococcus invades normally sterile sites such as the blood or central nervous system, causing bacteraemia or meningitis
There are more than 90 different types of pneumococci, known as serotypes, but only a small number actually cause pneumococcal disease. Therefore, understanding which serotypes cause disease can aid the development of appropriate vaccines.
A study published in 2010 found that 6 to 11 serotypes account for around 70% of cases of invasive pneumococcal disease (IPD) among children under 5 years old.
In the UK, before the introduction of the pneumococcal conjugate vaccine into the childhood schedule, the serotypes covered by the vaccine accounted for 73-100% of cases of IPD in the under 5s(2005-2006). This dramatically reduced to only 4% in 2008-2010 after the vaccine was launched.
Antibiotics are almost always used to treat pneumococcal infections. However, pneumococci are becoming increasingly resistant to commonly-used antibiotics. Therefore as pneumococcal bacteria become harder to treat, prevention by immunisation becomes even more important. The uses of vaccines coupled with prudent use of antibiotics are important if we are to see an impact on resistant pneumococci in the community.