Pneumococcus is a bacterium that colonizes the respiratory tract and can cause a range of illnesses—from mild ear infections and sinusitis to more serious, hospital-requiring conditions like pneumonia, bloodstream infections (sepsis), or meningitis.
The bacterium is surrounded by a protective polysaccharide capsule, with over 90 known capsule types (serotypes). Human immune defenses generate antibodies against these capsule polysaccharides—specific to each serotype. Only about 20 of these serotypes cause the majority of pneumococcal diseases.
Those most vulnerable to pneumococcal infections include children, the elderly, and individuals with chronic illnesses, often due to weaker or less mature immune systems. In many cases, pneumococcal infections follow a viral illness (e.g., the flu), which weakens mucosal defenses and makes it easier for the bacterium to establish infection.
Pneumococcus spreads via respiratory droplets—particularly through coughing and sneezing—and can also spread through contact. It is common for healthy individuals, especially young children, to carry pneumococcus in their nasal passages without showing symptoms. These asymptomatic carriers are the main vectors of transmission in the population.
In Finland, about 500,000 cases of middle ear infections (otitis media) occur annually. Over two-thirds are caused by bacteria, and pneumococcus is the most common bacterial culprit—particularly among children.
Pneumococcal infections can be prevented through vaccination. Finland’s national vaccination program offers pneumococcal vaccines to all children under the age of five. Booster doses are recommended for specific risk groups, including:
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