Introduction of PCV10 Reduces Vaccine-Type Pneumococcal Strains

In the first 3 years after the introduction of the pneumococcal conjugate vaccine 10 (PCV10), there was a significant reduction in the prevalence of PCV10 vaccine-type strains. Based on the study, investigators were able to link the observed changed in Global Pneumococcal Sequence Cluster prevalence with a decrease of infections caused by multidrug resistant pneumococci.¹

Further, after the introduction of the pneumococcal conjugate vaccine 10, investigators note a decrease of infections caused by multidrug resistance infection. | Image Credit: Jezper - stock.adobe.com

“Our findings indicate a significant reduction in PCV10-VT strains, along with a decrease in antibiotic resistance and the prevalence of piliated isolates,” the study authors said.¹ “Molecular analyses of the isolates examined enabled us to correlate these shifts in the prevalence of specific lineages associated with multidrug resistance, as well as a decline in lineages linked to higher virulence attributed to pili presence.”

In a study published in the International Journal of Infectious Diseases, the mortality trends for pneumococcal disease changed significantly following the onset of the COVID-19 pandemic. In early 2021, there were lower rates than normal followed by a spike in pneumococcus mortality in mid-2021. By the respiratory season of 2021, the pneumococcal mortality rates had returned to the normal seasonal trends prior to the COVID-19 pandemic. In another study, investigators found that the 10-valent pneumococcal conjugate vaccine reduced invasive disease for children and also provided indirect coverage for unvaccinated adults.^2,3

In the current study, investigators aimed to determine the changes in the population structure and genomic composition of pneumococcal strains for invasive infection for children under 2 years before and after PCV implementation in Poland. The study authors included all invasive pneumococcal isolates for children under 2 years in Poland between 2014 and 2020. There were 207 pneumococci collected, and 30 serotypes were detected. The most frequent serotypes were 19A, 14, 6B, 3, and 19F, which accounted for 46.4% of all the isolates. Prior to the introduction of PCV10, the most common serotypes were 6B, 19A, and 14, and post-PCV10, the most common were 3, 19A, and 14.¹

After the implementation of PCV10, there was a significant reduction in serotypes covered by the vaccine, with the prevalence decreasing from 56.9% in 2014 to 2016 to 29.5% in 2017 to 2020. From 2019 to 2020, the reduction was more pronounced, with PCV10 serotypes accounting for 18.6% of infections. Further, there was an increased prevalence of serotypes that were not included in PCV10, but the serotypes were covered by other available vaccines, according to the study authors. For other vaccines, the percentage of PCV13 serotypes increased from 17.6% prior to PCV vaccination to 25.7% post-PCV period. Further, serotypes for PCV20 increased from 7.8% to 18.2%, respectively, and PCV15 decreased slightly from 4.9% to 3.8%, respectively.¹

In the study population, the characterized resistance rates were 41.5% for penicillin, 49.3% for erythromycin, and 41.5% for clindamycin, according to the study authors. There were resistance levels of 23.2% observed for both cefotaxime and meropenem. As for multidrug resistance, investigators said that the most common resistance pattern for 38.2% of isolates was penicillin/cefotaxime/meropenem/erythromycin/clindamycin. This accounted for 44.2% of multidrug-resistant isolates.¹

“In the current study, we noticed changes in the level of antibiotic resistance after the implementation of PCV10,” the study authors said.¹ “We observed a significant decrease in resistance to penicillin, erythromycin, clindamycin, and chloramphenicol, as well as a decrease in multi-drug resistance.”

READ MORE: Pneumococcal Resource Center

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REFERENCES

1. Wróbel-Pawelczyk I, Gołębiewska A, Ronkiewicz P, et al. Changes in the Streptococcus pneumoniae population responsible for invasive disease of young children after the implementation of conjugated vaccines in the National Immunization Program in Poland. Vaccine. Published online September 19, 2025. doi:10.1016/j.vaccine.2025.127759

2. Nowosielski B. COVID-19 pandemic shows significant impact on pneumococcal mortality trends. Drug Topics. September 4, 2025. Accessed September 23, 2025. https://www.drugtopics.com/view/covid-19-pandemic-significantly-impacts-pneumococcal-mortality-trends

3. Nowosielski B. PCV10 among children indirectly protected unvaccinated adults. Drug Topics. August 28, 2025. Accessed September 23, 2025. http://drugtopics.com/view/pcv10-among-children-indirectly-protected-unvaccinated-adults