Clinical features of pneumococcal infection in children depending on vaccination status

Introduction. Pneumococcal infection remains one of the leading causes of respiratory disease in children. Despite the widespread implementation of pneumococcal conjugate vaccines, the impact of vaccination status on the clinical course of bacterial respiratory infections remains relevant. In the context of increasing antibiotic resistance of Streptococcus pneumoniae, the evaluation of approaches to antibiotic therapy in pediatric patients is of particular importance. The aim of the study was to assess the clinical and laboratory characteristics of pneumococcal infections and patterns of antibiotic therapy in children with different vaccination status.

Materials and methods. A retrospective study included 128 children aged of from 6 months to 6 years who received treatment for pneumonia, acute otitis media, or acute rhinosinusitis at the National Medical Research Center for Children’s Health (Moscow, Russia). Patients were divided into those vaccinated against S. pneumoniae (Group 1; n = 48) and unvaccinated children (Group 2; n = 80). Clinical parameters (disease severity, level and duration of fever), laboratory markers (leukocyte count, C-reactive protein, procalcitonin), and characteristics of antibiotic therapy (route of administration, choice of agent, duration of treatment) were evaluated.

Results. Severe disease forms were significantly more common in children of Group 2 (28.8% vs. 12.5%; p = 0.033). C-reactive protein levels were higher in the Group 2 (48 mg/L vs. 33 mg/L; p = 0.003), while leukocyte counts did not differ significantly. Oral antibiotic therapy predominated in both groups (87.5% and 80.0%), and amoxicillin/clavulanate was the first-line agent. Children of the Group 1 demonstrated a trend toward faster fever resolution (95.3% vs. 85.3%; p = 0.09).

Conclusion. Vaccination against S. pneumoniae is associated with milder clinical course, reduced inflammatory response, and lower prevalence of severe disease in children. Effective use of oral antibiotics supports the feasibility of managing most patients without parenteral therapy and highlights the importance of rational antibiotic selection.

Contribution:
Alacheva Z.A., Bakradze M.D., Lazareva A.V. — concept and design of the study;
Alacheva Z.A., Poliakova A.S., Yasakov D.S. — data collection and processing;
Alacheva Z.A., Yasakov D.S. — statistical processing of the data, writing the text;
Bakradze M.D., Lazareva A.V., Fisenko A.P. — editing the text.
All co-authors — approval of the final version of the article, responsibility for the integrity of all parts of the article.

Acknowledgment. The study had no sponsorship.

Conflict of interest. The authors declare no conflict of interest.

Received: November 10, 2025
Accepted: November 27, 2025
Published: December 25, 2025

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