Impact of the National Vaccination Strategy on the Prevalence of <i>Streptococcus pneumoniae</i> and Its Serotypes Among Clinically Healthy Children Under Six Years of Age During and After the COVID-19 Pandemic
Introduction: An effective vaccination strategy requires monitoring serotype changes by geography and age. This study analyzed <i>Streptococcus pneumoniae</i> serotypes in healthy children under 6 years of age vaccinated with PCV10 in Bulgaria from October 2021 to May 2025. Methods: A to...
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MDPI AG
2025-06-01
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| Online Access: | https://www.mdpi.com/2076-393X/13/6/634 |
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| author | Ivelina Trifonova Victoria Levterova Ivan Simeonovski Magi Ivanova Nadia Brankova Todor Kantardzhiev |
| author_facet | Ivelina Trifonova Victoria Levterova Ivan Simeonovski Magi Ivanova Nadia Brankova Todor Kantardzhiev |
| author_sort | Ivelina Trifonova |
| collection | DOAJ |
| description | Introduction: An effective vaccination strategy requires monitoring serotype changes by geography and age. This study analyzed <i>Streptococcus pneumoniae</i> serotypes in healthy children under 6 years of age vaccinated with PCV10 in Bulgaria from October 2021 to May 2025. Methods: A total of 569 children were screened for the <i>lytA</i> and <i>cpsA</i> genes viareal-time polymerase chain reaction (real-time PCR). Positive samples were typed using relevant kits, and 76 serotypes/serogroups of <i>S. pneumoniae</i> were identified. Results: Nasopharyngeal swabs from 232 children (40.8%) were found to carry <i>S. pneumoniae</i>, and a total of 255 serotypes were detected, with 19B/19C (17.2%), 6C (10.7%), and 15B/15C (9.8%) being the most prevalent. Of these, 91 serotypes (15.9%) were included in at least one vaccine, while the remaining 164 serotypes (25.4%) were not. The carriage rate reduced to 22% in 2023 but increased to 47% in 2024. Overall, younger children had lower carriage rates (<i>p</i> < 0.05), with serotype 6C being more common in children under 12 months of age (25%). Approximately 9.1% of pneumococcal carriage cases involved co-detected serotypes, with significantly higher co-detection rates for 19B/19C, 15B/15C, 10B, 10F/C, 23B, 7C/40, 23A, and 24A compared with mono-detection rates (<i>p</i> < 0.05). Conclusions: 19B/19C, 6C, 15B/15C, and 19A were identified as the main serotypes. Children over 3 years of age were also more likely to carry multiple pneumococci. These findings emphasize the need to reassess childhood vaccination strategies to curb the spread of antibiotic-resistant serotypes. |
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| institution | Matheson Library |
| issn | 2076-393X |
| language | English |
| publishDate | 2025-06-01 |
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| series | Vaccines |
| spelling | doaj-art-552c06eb67f84ca0a80c80c84b3d9ee02025-06-25T14:30:08ZengMDPI AGVaccines2076-393X2025-06-0113663410.3390/vaccines13060634Impact of the National Vaccination Strategy on the Prevalence of <i>Streptococcus pneumoniae</i> and Its Serotypes Among Clinically Healthy Children Under Six Years of Age During and After the COVID-19 PandemicIvelina Trifonova0Victoria Levterova1Ivan Simeonovski2Magi Ivanova3Nadia Brankova4Todor Kantardzhiev5National Centre of Infectious and Parasitic Diseases, 26 Yanko Sakazov Blvd., 1504 Sofia, BulgariaNational Centre of Infectious and Parasitic Diseases, 26 Yanko Sakazov Blvd., 1504 Sofia, BulgariaNational Centre of Infectious and Parasitic Diseases, 26 Yanko Sakazov Blvd., 1504 Sofia, BulgariaNational Centre of Infectious and Parasitic Diseases, 26 Yanko Sakazov Blvd., 1504 Sofia, BulgariaNational Centre of Infectious and Parasitic Diseases, 26 Yanko Sakazov Blvd., 1504 Sofia, BulgariaNational Centre of Infectious and Parasitic Diseases, 26 Yanko Sakazov Blvd., 1504 Sofia, BulgariaIntroduction: An effective vaccination strategy requires monitoring serotype changes by geography and age. This study analyzed <i>Streptococcus pneumoniae</i> serotypes in healthy children under 6 years of age vaccinated with PCV10 in Bulgaria from October 2021 to May 2025. Methods: A total of 569 children were screened for the <i>lytA</i> and <i>cpsA</i> genes viareal-time polymerase chain reaction (real-time PCR). Positive samples were typed using relevant kits, and 76 serotypes/serogroups of <i>S. pneumoniae</i> were identified. Results: Nasopharyngeal swabs from 232 children (40.8%) were found to carry <i>S. pneumoniae</i>, and a total of 255 serotypes were detected, with 19B/19C (17.2%), 6C (10.7%), and 15B/15C (9.8%) being the most prevalent. Of these, 91 serotypes (15.9%) were included in at least one vaccine, while the remaining 164 serotypes (25.4%) were not. The carriage rate reduced to 22% in 2023 but increased to 47% in 2024. Overall, younger children had lower carriage rates (<i>p</i> < 0.05), with serotype 6C being more common in children under 12 months of age (25%). Approximately 9.1% of pneumococcal carriage cases involved co-detected serotypes, with significantly higher co-detection rates for 19B/19C, 15B/15C, 10B, 10F/C, 23B, 7C/40, 23A, and 24A compared with mono-detection rates (<i>p</i> < 0.05). Conclusions: 19B/19C, 6C, 15B/15C, and 19A were identified as the main serotypes. Children over 3 years of age were also more likely to carry multiple pneumococci. These findings emphasize the need to reassess childhood vaccination strategies to curb the spread of antibiotic-resistant serotypes.https://www.mdpi.com/2076-393X/13/6/634<i>Streptococcus pneumoniae</i>19A6CPCV10serotypesvaccination |
| spellingShingle | Ivelina Trifonova Victoria Levterova Ivan Simeonovski Magi Ivanova Nadia Brankova Todor Kantardzhiev Impact of the National Vaccination Strategy on the Prevalence of <i>Streptococcus pneumoniae</i> and Its Serotypes Among Clinically Healthy Children Under Six Years of Age During and After the COVID-19 Pandemic Vaccines <i>Streptococcus pneumoniae</i> 19A 6C PCV10 serotypes vaccination |
| title | Impact of the National Vaccination Strategy on the Prevalence of <i>Streptococcus pneumoniae</i> and Its Serotypes Among Clinically Healthy Children Under Six Years of Age During and After the COVID-19 Pandemic |
| title_full | Impact of the National Vaccination Strategy on the Prevalence of <i>Streptococcus pneumoniae</i> and Its Serotypes Among Clinically Healthy Children Under Six Years of Age During and After the COVID-19 Pandemic |
| title_fullStr | Impact of the National Vaccination Strategy on the Prevalence of <i>Streptococcus pneumoniae</i> and Its Serotypes Among Clinically Healthy Children Under Six Years of Age During and After the COVID-19 Pandemic |
| title_full_unstemmed | Impact of the National Vaccination Strategy on the Prevalence of <i>Streptococcus pneumoniae</i> and Its Serotypes Among Clinically Healthy Children Under Six Years of Age During and After the COVID-19 Pandemic |
| title_short | Impact of the National Vaccination Strategy on the Prevalence of <i>Streptococcus pneumoniae</i> and Its Serotypes Among Clinically Healthy Children Under Six Years of Age During and After the COVID-19 Pandemic |
| title_sort | impact of the national vaccination strategy on the prevalence of i streptococcus pneumoniae i and its serotypes among clinically healthy children under six years of age during and after the covid 19 pandemic |
| topic | <i>Streptococcus pneumoniae</i> 19A 6C PCV10 serotypes vaccination |
| url | https://www.mdpi.com/2076-393X/13/6/634 |
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