What is Streptococcus pneumoniae?

The Streptococcus pneumoniae bacterium – also known as pneumococcus – is a common cause of respiratory tract inflammations, often accompanied by complications. This bacterium is widespread, especially among children in group settings.

Our research indicates that pneumococcus is present in the nasal mucosa of 40% of children. While this colonization often causes only mild symptoms like a runny nose or coughing, certain aggressive (invasive) strains can lead to serious pneumococcal diseases, including bacteraemia, meningitis, pneumonia, and middle ear infections.

Early symptoms of invasive pneumococcal disease

In its early stages, pneumococcal disease can present with nonspecific symptoms, such as:

• Deterioration of general condition

• Adynamia (lack of energy)

• Groaning and coughing

• Vomiting and abdominal pain

• Capillary bleeding under the skin

Why are preschool children at higher risk?

Preschool-aged children are particularly vulnerable to pneumococcal infections for several reasons:

1. Weaker immune response – The ability to produce antibodies against specific bacterial groups is still developing. The maturation of IgG2 antibodies, which play a key role in fighting polysaccharide-encapsulated bacteria, is not complete until the age of 12.

2. Frequent exposure to infections – Young children in kindergartens and playgroups are regularly exposed to new bacteria. Studies show that children in larger groups have three times higher risk of respiratory infections than those who stay at home.

3. Hygiene habits – Unlike older children, preschoolers may not yet have developed proper hygiene habits, increasing the spread of infection through dirty hands, nasal and oral secretions, and shared personal items.

The link between group settings and infection rates

Research has consistently shown a strong connection between early group exposure and higher infection rates:

• Children in kindergartens get sick twice as often as those in smaller family groups (3-6 children).

• The risk is higher in urban areas compared to rural settings.

• A Swedish study found that children in traditional kindergartens experience more respiratory infections than those in home-based care.

Who Is most at risk for pneumococcal disease?

While anyone can contract pneumococcus, certain groups are at a higher risk of severe complications:

• Children under 5 years (especially in group settings)

• Elderly adults over 50 years

• Individuals with chronic diseases (heart, lung, kidney diseases, diabetes)

• Patients with weakened immune systems

• People suffering from alcoholism or malignancies

The importance of pneumococcal vaccination

Vaccination against S. pneumoniae is one of the most effective ways to prevent severe forms of pneumococcal disease. Due to the growing antibiotic resistance of pneumococcus, immunization is now a recommended preventive measure.

Introduction to pneumococcal immunisation

The 23-valent pneumococcal vaccine is well known and requires no special introduction here. It should be noted that the ability to create specific antibodies against membrane polysaccharides is very small among children below 2 years of age (the dynamic of IgG2 maturation).

Types of pneumococcal vaccines

Several years ago, the 13-valent conjugate vaccine appeared on the market. Aimed against invasive streptococcus pneumoniae serotypes 13 (Prevenar 13 – registered for ages 6 weeks and over) and 10 (Synflorix – for children aged 6 weeks to 5 years), it provides a high level of protection against invasive forms of this disease (inflammation of the brain and brain membranes, bacteraemia).

Benefits of the 13-valent vaccine

Unlike its 23-valent counterpart, the 13-valent vaccine also decreases the possibility of the child becoming a carrier. This provides indirect protection for younger siblings who do not form part of a group and have not yet been immunised. Furthermore, unlike conjugate vaccines, the 23-valent polysaccharide vaccine does not reduce the frequency of middle ear infections caused by pneumococcus.

Impact of immunisation on disease prevention

Since previous years have seen a rise in the frequency of resistant traits of pneumococcus, specific immunisation is becoming increasingly important. In addition to reducing invasive forms of pneumococcal diseases and middle ear infections, immunisation with a 13-valent vaccine significantly lowers the frequency of pneumonia (especially severe cases).

Immunisation of children indirectly reduces the frequency of pneumococcal disease among elderly family members (grandparents). As an illustration of its epidemiological effect, consider the case of the US, where immunisation with a 7-valent conjugate vaccine was introduced in 2000 and replaced with a 13-valent vaccine in 2010. The frequency of invasive pneumococcal infections among children below five was reduced by 64% with the 7-valent vaccine and by 93% with the 13-valent vaccine. Among adults, the 13-valent vaccine led to a decrease of 58–72% (depending on the age group) in invasive pneumococcal infections.

Pneumococcal immunisation in Croatia

Pneumococcal isolate serotyping in Croatia has shown that there are no significant differences in the presence of individual types compared to the US and European countries. Introducing the vaccine into the regular immunisation programme may lead to an estimated 83% (10-valent vaccine) or 90% (13-valent vaccine) decrease in invasive pneumococcal disease.

Guidelines for at-risk populations

The 2014–2016 immunisation, seroprophylaxis, and chemoprophylaxis programme for special groups and individuals under increased risk includes recommendations for protection against invasive pneumococcal forms.

“Pneumococcal diseases: conjugate polysaccharide vaccine for children aged 2 months to five years and adults over 50 (for children aged two months to five years: splenectomised, with congenital heart defects, chronic metabolic diseases including diabetes, immunodeficiency, malignant diseases, surgery – cochlear implants and ventriculoperitoneal shunts, as well as severe chronic diseases of the lungs, kidneys, and liver; for persons older than 50: chronic metabolic diseases including diabetes, immunodeficiency, malignant diseases and severe chronic diseases of the lungs, kidneys, and liver).”

Conclusion and recommendations

In our daily work, it is necessary to ensure that patients belonging to groups defined by the Programme exercise their rights and receive adequate protection. Conjugate vaccine immunisation (13-valent conjugate vaccine, the only vaccine registered for use in this age group) is recommended among patients aged 6 to 49 carrying the risk factors described above. Additional 23-valent polysaccharide vaccine immunisation may also be considered for individuals over the age of two.

Detailed information on the vaccine along with a description of its characteristics is available on the HALMED (Agency for Medicinal Products and Medicinal Devices of Croatia) and EMA (European Medicines Agency) websites.¹⁶

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