Streptococcus pneumoniae is a cause of significant morbidity and mortality worldwide. There are many different serotypes of the organism which may be carried by up to 50% of children under the age of 6 years, as well as many adults. The organism is associated with both pneumonia and invasive pneumococcal disease, which may result in septicemia or meningitis. It is also a principal cause of otits media and sinusitis, which are not life-threatening, but generate a lot of discomfort, loss of schooling or working days, and around 60 000 GP consultations per year in the UK. Vaccination is a safe and effective way to prevent this infection from causing significant ill health.