PCV10 Among Children Indirectly Protected Unvaccinated Adults

The 10-valent pneumococcal conjugate vaccine (PCV10) reduced invasive pneumococcal disease (IPD) among children and provided indirect protection for unvaccinated adults, according to a study published in Frontiers in Public Health.¹ The researchers’ findings highlight how pneumococcal serotype surveillance is crucial for vulnerable populations.

“PCVs have been in use for more than 20 years with increasing global coverage,” wrote authors of a study published in the Journal of Global Health.² “By the end of 2019, PCVs had been introduced in 149/195 (76%) countries and global coverage was estimated to be 48%.”

In recent history, PCV development has been significant, with new valencies commonly being approved for use in adults and children. In the US, several PCV formulations have been approved for adult, adolescent, and pediatric populations. Alongside the pneumococcal polysaccharide vaccine (PPSV23), there are 3 PCVs available for children and adults: PCV15, PCV20, and PCV21.³

PCV10 was introduced into Lithuania's NIP in October of 2014. | image credit: Ben Gingell / stock.adobe.com

In Lithuania, where the current study was conducted, PCV10 was introduced into the national immunization program (NIP) in October of 2014. Similar to the US, Lithuania’s NIP updated these schedules more recently, adding PCV15 for children and PCV20 for at-risk pediatric and adult populations.¹

READ MORE: Increased Vaccination Could Curb Burden of Community-Acquired Pneumonia

However, amid these PCV recommendation changes, researchers are trying to uncover further evidence on the impact of PCV10 regarding IPD outcomes and incidence among Lithuanian children and adults. Aiming to find the prevalence of pneumococcal carriage among these populations, as well as the most common serotypes uncovered, researchers explored how PCV10 impacts Lithuanian patients.

“We aimed to assess the impact of PCV10 on the distribution of IPD serotypes in Lithuania across the overall population and specific age groups, covering the pre-vaccination period (2010-2014) and the post-vaccination period (2015-2024),” wrote authors of the current study.¹

Researchers conducted a retrospective study exploring invasive Streptococcus pneumoniae (S. pneumoniae) isolates over 2 timeframes: the pre-PCV10 period (2010–2014) and the post-PCV10 period (2015–2024). In the context of this study, these periods were referred to as the pre- and post-vaccine periods, denoting when PCV10 was added to Lithuania’s NIP. Using these S. pneumoniae isolate data, researchers analyzed overall serotype distribution among Lithuania’s population and then determined the separate distribution of serotypes among children and adults.

Based on the 1190 invasive pneumococcal isolates collected by the National Public Health Surveillance Laboratory, researchers discovered that these isolates far outweighed reports of IPD. Among those who contracted the IPD isolates but were never diagnosed, the incidence of IPD may have gone underreported. Highlighting effectiveness of the recommended vaccine, PCV10 serotypes decreased significantly, from 50% in 2010 to 2014, to 20% in 2024.

They also found trends in the distribution of specific serotypes, with 19A, 3, and 6C showing increasing trends among non-PCV10 serotypes. Serotypes 8 and 22F increased the most among PCV10 serotypes. Following the results, they noted that serotype 3 remains the most prominent PCV serotype since 2015.

“After the nationwide implementation of PCV10 for childhood immunization in 2014, a marked decline in PCV10 serotypes was observed across the entire population, consistent with trends reported in other countries after vaccine introduction,” continued the authors.¹ “In children, the significant decline provides strong evidence of direct vaccine impact.”

These results highlight the overall effectiveness of PCV10 in Lithuania since its implementation into the NIP. Not only did increases in PCV10 use translate to greater serotype reduction among children, but similar trends were also highlighted among adults 18 and up. On top of benefits outside of pediatric populations, data also showed decreased serotypes and added protection against IPD among individuals who were not vaccinated.

However, with some serotypes still appearing more often than others, there is still an apparent need to conduct serotype surveillance and monitor emerging or increasing serotypes. As PCVs increase in valency and efficacy, researchers will continue to map out serotype pathways.

“Our study provides evidence of an indirect effect of the childhood PCV10 vaccination in the adult population in Lithuania, most of whom did not receive the vaccine,” concluded authors of the study.¹ “These findings underscore the importance of ongoing pneumococcal serotype surveillance to monitor the emergence and expansion of non-vaccine serotypes, such as 19A, which are included in higher-valency vaccines and pose a particular risk to vulnerable populations, especially older adults.”

READ MORE: Pneumococcal Resource Center

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References

1. Petrutienė A, Sinotova J, Pupienienė N, et al. A decade of 10-valent pneumococcal conjugate vaccine use in Lithuania: trends in invasive pneumococcal serotype dynamics. Front Public Health. 2025 Aug 1;13:1633396. doi: 10.3389/fpubh.2025.1633396.

2. Reyburn R, Tsatsaronis A, von Mollendorf C, et al. Systematic review on the impact of the pneumococcal conjugate vaccine ten valent (PCV10) or thirteen valent (PCV13) on all-cause, radiologically confirmed and severe pneumonia hospitalisation rates and pneumonia mortality in children 0-9 years old. J Glob Health. 2023 Feb 3;13:05002. doi: 10.7189/jogh.13.05002.

3. Types of pneumococcal vaccines. CDC. September 12, 2024. Accessed August 28, 2025. https://www.cdc.gov/pneumococcal/vaccines/types.html