There are more than 90 different types of pneumococci, known as serotypes, but only a small number actually cause pneumococcal disease. Understanding which serotypes cause disease can aid the development of appropriate vaccines.

A recent review of the literature 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 70% of cases of IPD in the under 5’s (2005-2006). This dramatically reduced to only 24% in 2007-2008 after the vaccine was launched.

A number of factors including age, comorbid conditions and clinical presentation can all affect serotype distribution and mortality. A study in Denmark of more than 18,000 patients with IPD found that serotypes 31, 11A, 35F, 17F, 3, 16F, 19F, 15B and 10A were associated with highly increased mortality compared with serotype 1.

Antibiotics are almost always used to treat pneumococcal infections. However, there is concern that pneumococci are becoming increasingly resistant to commonly- used antibiotics. As pneumococcal bacteria become harder to treat because of this resistance, prevention of pneumococcal disease 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.

To read more about serotypes and vaccination pneumococcal disease click here .

Key points

• Pneumococcal disease is spread by the bacterium Streptococcus pneumoniae
  
• In 2008, pneumococcal disease killed up to 12,750 people in the UK over the age of 65
• There are more than 90 different types of pneumococci, known as serotypes