Modern Pediatrics. Ukraine. (2026).3(155): 26-34. doi: 10.15574/SP.2026.3(155).2634
Volokha A. P.¹, Bondarenko A. V.², Hilfanova A. M.², Stepanovskiy Yu. S. ², Yanovska V. V.³, Anopriienko O. V.⁴, Yakimovych S. A.⁵, Zlotnikova O. V.⁶, Nekhaienko M. I.⁷, Savchak I. Ya.⁸, Grabovska I. V.⁹, Kosovska T. V.¹⁰, Boyarchuk O. R.^10
1Shupyk National Healthcare University of Ukraine, Kyiv
²First European University, Kyiv, Ukraine
³Public Health Center of the Ministry of Health of Ukraine, Sector of Bacteriological Research Reference laboratories for diagnostics of tuberculosis, bacterial, parasitic and especially dangerous pathogens, Kyiv
⁴Institute of Molecular Biology and Genetics of National Academy of Sciences of Ukraine, Laboratory of Biosynthesis of Nucleic Acids, Kyiv
⁵Medical Center “Doctor Sam”, Kyiv, Ukraine
⁶Fayna Klinika, Kyiv, Ukraine
⁷МNE Dymer Central Clinic, Ukraine
⁸МNE of Lviv Regional Council "Clinical Center of Pediatric Medicine" JV "Western Ukrainian Specialized Center", Ukraine
⁹NE "Volyn Regional Territorial Medical Association for the Protection of Motherhood and Childhood”, Lutsk, Ukraine
⁰I. Hopbachevskyi Ternopyl National Medical University, Ukraine

For citation: Volokha AP, Bondarenko AV, Hilfanova AM, Stepanovskiy YuS, Yanovska VV, Anopriienko OV et al. (2026). Serotype landscape of Streptococcus pneumoniae in nasopharyngeal colonization in children aged 6 months to 5 years in Ukraine (updated data 2021-2025). Modern Pediatrics. Ukraine. 3(155): 26-34. doi: 10.15574/SP.2026.3(155).2634.
Article received: Dec 21, 2025. Accepted for publication: Apr 13, 2026.

Streptococcus pneumoniae (S. pneumoniae) remains the leading cause of childhood mortality worldwide. The current landscape of pathogen serotypes is an important tool for planning the future national immunization program (NIP), but this issue has not been studied sufficiently in Ukraine.
Aim – to study the level of nasopharyngeal colonization with pneumococci in children aged 6 months to 5 years in Ukraine, the distribution of S. pneumoniae serotypes.
Materials and methods. A prospective observational study of nasopharyngeal carriage of pneumococci was conducted in the period 2021-2025. One thousand and thirty one healthy children aged 6 months to 4 years 11 months 30 days were examined. Nasopharyngeal mucus samples were taken once by the deep transnasal swab. Real-time polymerase chain reaction (PCR) was used to identify serotypes of S. pneumoniae.
Results. The overall incidence of nasopharyngeal pneumococcal colonization among children aged 6 months to 5 years was 7%, increased to 18% in the period after the COVID-19 pandemic. Among the selected pneumococcal strains, 49.4% belonged to capsular, of which 9 different serotypes were identified: 4, 6A, 6B, 7A/7F, 9V, 11A/D, 18, 19F, 23F. Dominated pneumococcal serotypes 6A (33%), 19F (25%), 23F (16.7%), 18 (8.3%). Statistically proven risk factors for pneumococcal carriage among children aged 6 months to 5 years were the presence of siblings and sharing a bedroom with other children.
Conclusions. The level of nasopharyngeal carriage of pneumococci in children under 5 years of age in Ukraine decreased during the COVID-19 pandemic, but an increase in the level of carriage has been noted in the post-pandemic period. Among the typed pneumococcal serotypes, 97.3% were covered by the pneumococcal conjugate 13-valent vaccine (PCV13). The results of studies on the distribution of pneumococcal serotypes in Ukraine were consistent with data on nasopharyngeal carriage of pneumococci, as in other countries in Europe and America before the introduction of the PCV vaccine into the NIP.
The research was carried out in accordance with the principles of the Helsinki Declaration. The informed consent of the patients was obtained for conducting the studies.
No conflict of interests was declared by the authors.
Keywords: pneumococcus, S. pneumoniae, children, nasopharyngeal carriage, nasopharyngeal colonization, serotypes, seroepidemiology, serotype distribution (landscape).

REFERENCES

1. Carvalho Mda G, Tondella ML, McCaustland K, Weidlich L, McGee L, Mayer LW et al 2007. Evaluation and improvement of real-time PCR assays targeting lytA, ply, and psaA genes for detection of pneumococcal DNA. J Clin Microbiol. 45: 2460-2466. https://doi.org/10.1128/JCM.02498-06; PMid:17537936 PMCid:PMC1951257

2. CDC. (2010). Prevention of Pneumococcal Disease Among Infants and Children – Use of 13-Valent Pneumococcal Conjugate Vaccine and 23-Valent Pneumococcal Polysaccharide Vaccine: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR. 59 (RR-11). URL: http://www.cdc.gov

3. Ceyhan M, Karadag-Oncel E, Hascelik G et al. (2021). Nasopharyngeal carriage of Streptococcus pneumoniae in healthy children aged less than five years. Vaccine, 39: 2041-2047. https://doi.org/10.1016/j.vaccine.2021.03.028; PMid:33741188

4. Chernyshova LI, Hilfanova AM, Bondarenko AV ta in. (2014). Rozpodil serotypiv Streptococcus pneumonia pry nazofarynhealnomu nosiistvi u zdorovykh ditei vikom vid 6 misiatsiv do 5 rokiv v Ukraini. Sovremennaia pedyatryia. 4(60): 77-83.

5. ECDC. (2022). Invasive Pneumococcal Disease. Annual Epidemilogical Report for 2022. URL: http://www.ecdc.gov.

6. Horvát A, Huber A, BarthaA et al. (2025). Pneumococcal carriage among young children attending daycare in Hungary, 12-13 years post-PCV13: a cross-sectional study. Scientific Reports. 15: 22696. https://doi.org/10.1038/s41598-025-07777-x; PMid:40593220 PMCid:PMC12215634

7. Lewnard JA, Hanage WP. (2019). Making sense of differences in pneumococcal serotype replacement. Lancet Infect Dis. 19: e213-220. https://doi.org/10.1016/S1473-3099(18)30660-1; PMid:30709666

8. Mavroidi A, Godoy D, Aanensen DM, Robinson DA, Hollingshead SK, Spratt BG. (2004). Evolutionary genetics of the capsular locus of serogroup 6 pneumococci. J. Bacteriol. 186: 8181-8192. https://doi.org/10.1128/JB.186.24.8181-8192.2004; PMid:15576766 PMCid:PMC532438

9. Mrabt F, Guedes S. (2025). Systematic review on serotypes distribution of pneumococcal pneumonia in adults and the elderly. BMC Public Health. 25: 1194. https://doi.org/10.1186/s12889-025-22164-x; PMid:40158111 PMCid:PMC11954302

10. Neal EFG, Chan J, Nguyen CD, Russell FM. (2022). Factors associated with pneumococcal nasopharyngeal carriage: A systematic review. PLOS Glob Public Health. 2(4): e0000327. https://doi.org/10.1371/journal.pgph.0000327; PMid:36962225 PMCid:PMC10021834

11. Neves FPG, Pinto TCA, Corrêa MA et al. (2013). Nasopharyngeal carriage, serotype distribution and antimicrobial resistance of Streptococcus pneumoniae among children from Brazil before the introduction of the 10-valent conjugate vaccine. BMC Infectious Diseases. 13: 318. https://doi.org/10.1186/1471-2334-13-318; PMid:23849314 PMCid:PMC3718621

12. Petrović V, Milosavljevi B, Djilas M et al. (2022). Pneumococcal nasopharyngeal carriage in children under 5 years of age at an outpatient healthcare facility in Novi Sad, Serbia during the COVID-19 pandemic. IJID Regions. 4: 88-96. https://doi.org/10.1016/j.ijregi.2022.07.001; PMid:35865274 PMCid:PMC9294645

13. Pimenta FC, Roundtree A, Soysal A, Bakir M, du Plessis M, Wolter N et al. (2013, Feb). Sequential triplex real-time PCR assay for detecting 21 pneumococcal capsular serotypes that account for a high global disease burden. J Clin Microbiol. 51(2): 647-652. Epub 2012 Dec 5. https://doi.org/10.1128/JCM.02927-12; PMid:23224094 PMCid:PMC3553924

14. Rafei R, Zaylaa M, Diab M et al. (2025). Nasopharyngeal Carriage, Antimicrobial Resistance, and Serotype Distribution of Streptococcus pneumoniae in Children Under Five in Lebanon: Baseline Data Prior to PCV13 Introduction. Antibiotics. 14: 168. https://doi.org/10.3390/antibiotics14020168; PMid:40001412 PMCid:PMC11851980

15. Safari D, Daningrat WOD, Milucky JL et al. (2024). Nasopharyngeal carriage of Streptococcus pneumoniae among children <5 years of age in Indonesia prior to pneumococcal conjugate vaccine introduction. PLoS ONE. 19(1): e0297041. https://doi.org/10.1371/journal.pone.0297041; PMid:38206916 PMCid:PMC10783721

16. Trifonova I, Levterova V, Simeonovski I, Ivanova M, Brankova N, Kantardzhiev T. (2025). Impact of the National Vaccination Strategy on the Prevalence of Streptococcus pneumoniae and Its Serotypes Among Clinically Healthy Children Under Six Years of Age During and After the COVID-19 Pandemic. Vaccines. 13: 634. https://doi.org/10.3390/vaccines13060634; PMid:40573965 PMCid:PMC12197779

17. Tvedskov ESF, Hovmand N, Benfield T, Tinggaard M. (2022). Pneumococcal carriage among children in low and lower-middle-income countries: A systematic review. International Journal of Infectious Diseases. 115: 1-7. https://doi.org/10.1016/j.ijid.2021.11.021; PMid:34800691

18. Wang L, Fu J, Liang Z, Chen J. (2017). Prevalence and serotype distribution of nasopharyngeal carriage of Streptococcus pneumoniae in China: a meta-analysis. BMC Infectious Diseases. 17: 765. https://doi.org/10.1186/s12879-017-2816-8; PMid:29237402 PMCid:PMC5729489

19. Wróbel-Pawelczyk I, Ronkiewicz P, Wanke Rytt M et al. (2022). Pneumococcal carriage in unvaccinated children at the time of vaccine implementation into the national immunization program in Poland. Scientific Reports. 12: 5858. https://doi.org/10.21203/rs.3.rs-810749/v1

20. World Health Organization. (2012). Pneumococcal vaccines WHO position paper – 2012. Weekly epidemiological record. 87(14): 129-144.