Pneumococcal infections are acute infections caused by the Streptococcus pneumoniae (S. pneumoniae) bacterium. There are more than 90 different strains of S. pneumoniae bacteria, which are known as serotypes.
S. pneumoniae enters the human body through the nose and mouth.
Types of pneumococcal infection
Pneumococcal infections usually fall into one of the following two categories.
- Non-invasive pneumococcal infections. These occur outside the major organs or the blood and tend to be less serious.
- Invasive pneumococcal infections. These occur inside a major organ or the blood and tend to be more serious.
The two types of infection are described in more detail below.
Non-invasive pneumococcal infections
Non-invasive pneumococcal infections include the following.
- bronchitis: an infection of the bronchi, which are the tubes that run from the windpipe down into the lungs
- otitis media: an infection of the middle ear, which usually affects children under the age of 10
- sinusitis: an infection of the sinuses, the small air-filled cavities behind the cheekbones and forehead
Invasive pneumococcal infections
Invasive pneumococcal infections include the following.
- bacteraemia: a relatively mild infection of the blood
- septicaemia (blood poisoning): a more serious blood infection
- osteomyelitis: infection of the bone
- septic arthritis: infection of a joint
- pneumonia: infection of the lungs
- meningitis: infection of the meninges, which are the protective membranes surrounding the brain and spinal cord
How common are pneumococcal infections?
It is difficult to estimate the exact number of cases of non-invasive pneumococcal infections that occur each year in England. This is because infections often clear up within a few days and many people do not visit their GP. However, they are thought to be quite common.
One estimate is that there are around 63,000 cases of otitis media associated with pneumococcal infections in England and Wales each year.
Pneumonia is the most common type of invasive pneumococcal infection. Each year in England and Wales an estimated 40,000 people are admitted to hospital to be treated for pneumonia.
Other types of invasive pneumococcal infections, such as bacteraemia, are less common, with around 5,000 to 6,000 cases reported each year.
Meningitis is the most serious type of invasive pneumococcal infection and is also the rarest. It is estimated that only 1 person in every 100,000 will develop meningitis in any given year in England.
People with a weakened immune system are most at risk of catching a pneumococcal infection. This may be because:
- they have a serious health condition, such as HIV or diabetes, that weakens their immune system
- they are having treatment or taking medication that weakens their immune system, such as chemotherapy
Other at-risk groups include:
- babies and young children under two years of age
- adults over 65 years of age
- people who misuse alcohol
See Pneumococcal infections - causes for a full list of the groups who are at risk of developing a pneumococcal infection.
Cases of invasive pneumococcal infection usually peak in the winter during December and January.
Pneumococcal infections can be treated with antibiotics.
Pneumococcal vaccines
There are two different types of pneumococcal vaccine:
- pneumococcal conjugate vaccine (PCV), which is given to all children under two years of age as part of the childhood vaccination programme
- pneumococcal polysaccharide vaccine (PPV), which is given to people aged 65 years or over and others who are at high risk
The PCV protects against 13 types of S. pneumoniae bacteria and the PPV protects against 23 types. It is thought that the PPV is around 50-70% effective at preventing more serious types of invasive pneumococcal infection.
See Pneumococcal vaccination - how it works for more information about these two types of vaccine and Pneumococcal vaccination - when it is used for further details of the high-risk groups that should receive the vaccine.
Outlook
Non-invasive pneumococcal infections are usually mild and go away without the need for treatment.
The outlook for pneumonia in people who are otherwise healthy is good, but the infection can lead to serious complications in people who are very young, very old or have another serious health condition.
However, due to the introduction of the PCV in 2002, the number of people dying from complications that arise from pneumonia has fallen to around 7%.
The outlook for other types of invasive pneumococcal infections such as bacteraemia is generally good, although there is about a 1 in 20 chance that bacteraemia will trigger meningitis as a secondary infection.
The outlook for meningitis is poor. One person in ten with the condition will die and one in four will experience complications such as hearing loss, which may be permanent.
