Pneumococcal Conjugate Vaccine Booster Maximizes Protection Against IPD

Pneumococcal conjugate vaccines (PCVs) were deemed highly effective in preventing invasive pneumococcal disease (IPD) among children, according to a study published in Vaccine: X.¹ The study also revealed that PCV booster doses play a key role in maximizing vaccine type-IPD protection within the same population.

“Streptococcus pneumoniae is a bacterial pathogen responsible for a wide range of diseases, from mucosal infections, such as otitis media, sinusitis, and pneumonia, to IPD, which includes bacteremic pneumonia, sepsis, and meningitis,” wrote the authors of the study. “High-risk populations include children under 5 years, adults over 65 years, individuals with immunocompromising conditions, those with chronic comorbidities, and individuals with lifestyle risk factors such as smoking, alcohol misuse, and being unhoused.”

According to CDC data, IPD incidence falls at 8.3 cases per 100,000 patients. Further stratifying these statistics, the average mortality rate was 1 death per 100,000. Accounting just for children under the age of 18, this age group’s incidence rate was 6.9 per 100,000. Finally, these data also showed a trend of greater risk for IPD complications as ages were reported to be lower.²

Despite the continued prominence of IPD, especially among older adults and pediatric patients, its common occurrence has been significantly ameliorated through the introduction of PCVs.

READ MORE: Introduction of PCV10 Reduces Vaccine-Type Pneumococcal Strains

Indeed, after the US’ implementation of PCV7 in 2000,³ rates of pediatric IPD have decreased significantly. Because of vaccine protection against IPD, childhood rates of the disease decreased by 72% from 2002 to 2021.⁴ Since the introduction of all new PCVs following PCV7, researchers are still trying to determine the proper dosing and administration of PCVs to maximize protection against pediatric IPD.

“While previous research has evaluated overall [vaccine effectiveness (VE)], the impact of different pneumococcal dosing regimens remains unclear,” they continued.¹ “Given the importance of optimizing pneumococcal vaccination strategies, we aim to evaluate the effectiveness of PCV7 and PCV13 based on the number of vaccine doses received in this systematic review and meta-analysis.”

To go about reassessing PCV7 and PCV13, researchers conducted a systematic review and meta-analysis of studies that explored the VE of each PCV valency among patients 18 years and younger.

More specifically, to determine VE among this population, researchers separated participating patients into 4 groups based on vaccination status at the onset of children’s IPD. The 4 groups were a primary plus booster group (1 to 3 primary doses less than 12 months of age plus 1 booster dose 12 months or greater); the 1 primary dose group; 2 primary doses group; and 3 primary doses group (primary doses given <12 months of age and no booster).

With patients telling providers their vaccination status while also reporting IPD, the researchers were better able to determine how effective they were and what the ideal PCV dose should be.

After identifying 1982 studies on their initial search, study experts concluded their review with a total of 25.

“Pooled results showed that children receiving 2 or 3 primary doses without a booster had a higher risk of IPD compared with those completing a schedule with a booster dose (2 + 1 or 3 + 1 schedules),” wrote the authors.¹ “Our findings reinforce the existing evidence supporting a vaccination schedule that includes a booster dose, as we found neither 2 nor 3 primary doses alone consistently achieved a pooled VE of >90% as with a schedule including a booster dose.”

Previous evidence has shown that IPD can occur in vaccinated individuals due to PCV7 and PCV13’s inability to protect against vaccine serotypes 3 and 19A. However, with the current finding of the booster’s significant success over 1, 2, or even 3 doses of the primary vaccine alone, researchers uncovered an ideal PCV regimen for keeping children protected against IPD. As long as primary vaccine doses are accompanied by a subsequent booster, children 18 years and under can become even better protected against IPD.

“Our study reaffirms the high overall effectiveness of PCVs in preventing IPD in children and highlights the essential role of the booster dose in maximizing protection against [vaccine type]-IPD,” concluded the authors.¹ “As many countries transition to reduced dosing schedules to improve cost-effectiveness, streamline immunization programs, and address vaccine supply constraints, our findings emphasize the need for a full vaccination series that includes a booster to ensure optimal protection against IPD.”

READ MORE: Pneumococcal Resource Center

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REFERENCES

1. Chang CY, Nasreen S, Sadarangani M, et al. Effectiveness of vaccine dosing schedules for pneumococcal invasive disease in children: a systematic review and meta-analysis. Vaccine X. 2025;27:100734. https://doi.org/10.1016/j.jvacx.2025.100734

2. Chapter 11: pneumococcal. CDC. January 17, 2025. Accessed October 7, 2025. https://www.cdc.gov/surv-manual/php/table-of-contents/chapter-11-pneumococcal.html

3. Progress in introduction of pneumococcal conjugate vaccine — worldwide, 2000–2008. CDC. October 24, 2008. Accessed October 7, 2025. https://www.cdc.gov/mmwr/preview/mmwrhtml/mm5742a2.htm

4. Yildirim I, Lapidot R, Shaik-Dasthagirisaheb YB, et al. Invasive pneumococcal disease after 2 decades of pneumococcal conjugate vaccine use. Pediatrics. 2023;153(1):e2023063039. https://doi.org/10.1542/peds.2023-063039