Pneumococcal disease includes a wide range of infections caused by different types of pneumococcus bacteria (Streptococcus pneumoniae). There are over 90 different types of these bacteria, and vaccines have been produced to protect against the types that cause the most disease.
These bacteria are the most common cause of pneumonia, a serious illness which can affect people of any age. In the UK, around 40,000 people a year are hospitalised with pneumococcal pneumonia. Even with the use of antibiotics, pneumonia still causes death in up to 20% of cases. Worldwide, pneumonia is the leading cause of death in children. According to the World Health Organization, pneumonia killed over 920,000 children in 2015, and accounts for 16% of all deaths of children under 5 years old. Pneumonia can be caused by a number of different bacteria, viruses and fungi. However, it is estimated that at least two thirds of all cases of bacterial pneumonia are caused by Streptococcus pneumoniae bacteria.
Certain types of pneumococcus bacteria can also infect normally sterile areas of the body such as the blood and the brain. This is called invasive pneumococcal disease, and causes life-threatening diseases including septicaemia (severe blood poisoning) and meningitis (inflammation of the outer covering of the brain and spinal cord). Around 15% of children with pneumococcal meningitis die, and 25% will have severe, lasting effects, including loss of hearing, loss of sight, learning and language disabilities, or seizures. Invasive pneumococcal disease particularly affects very young babies, elderly people and those with weakened immune systems. People with cochlear implants, cerebrospinal fluid (CSF) leaks, skull defects or fractures of the skull can sometimes get repeated infections.
Pneumococcal disease can also cause ear infections (otitis media) and sinusitis.