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Pneumococcal disease

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.

Burden of Disease & Transmission

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.  

The most frequent manifestation of pneumococcal disease is pneumococcal pneumonia where the pneumococcus may be responsible for up to 60 % of cases of community-acquired pneumonia (CAP). The impact of pneumococcal disease in the UK is substantial with approximately 6000 cases of IPD reported annually and 192,281 hospital admissions for pneumonia in 2013/14 in England of which up to 50 % may be pneumococcal. The cost to the UK National Health Service is estimated at more than £1 billion.

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, invasive pneumococcal disease killed 43 children (aged 1 month to 4 years) 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.

Vaccine Impact

In England and Wales, prior to the introduction of the pneumococcal conjugate vaccine (Prevenar*, Pneumococcal polysaccharide conjugate vaccine (7-valent), PCV7) to the national immunisation programme (NIP), the incidence of invasive pneumococcal disease (IPD) was highest in <2-year-olds (36/100000 in 2005–2006) and the serotypes included in PCV7 were responsible for 73% of IPD  

  • Since the introduction of PCV7 to the NIP in 2006, in England and Wales there has been an overall 37% reduction in IPD incidence  
  • There has been a further  7% reduction since  the introduction of Prevenar 13.  
  • It has been estimated that almost  40,000 cases of IPD have been prevented since the start of the pneumococcal conjugate vaccine programme  

Post Prevenar® introduction there has been a decline in hospitalisations for bacterial pneumonia and empyema in children <15 years  and a further reduction in hospitalisations for empyema in the under 2s.  

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. 

 

*A 7-valent vaccine (Prevenar) was introduced in 2006 and replaced by Prevenar 13® in 2010.