Early Data Show Decline in PCV20-Added Serotypes Among Children With Invasive Pneumococcal Disease

Early surveillance data presented at IDWeek 2026 in Washington, DC, suggest that the share of invasive pneumococcal disease (IPD) caused by the 7 serotypes added in the pneumococcal 20-valent conjugate vaccine (PCV20; Prevnar 20; Pfizer) has declined among children aged younger than 24 months since the vaccine was recommended for routine use in US infants.^1,2 The findings come from a multicenter surveillance study of US children’s hospitals, presented by Kristina Hultén, PhD, professor in the Department of Pediatrics, Division of Infectious Disease, at Baylor College of Medicine and Texas Children’s Hospital.²

Background on Expanded-Valency Vaccines

PCV20 adds serotypes 8, 10A, 11A, 12F, 15B, 22F, and 33F to the serotypes covered by PCV13.¹ PCV15, which adds 22F and 33F to PCV13, was recommended for children in June 2022. PCV20 followed in June 2023.^1,3 The investigators noted that maternal respiratory syncytial virus (RSV) immunization and infant nirsevimab (Beyfortus; Sanofi, AstraZeneca) were also recommended in 2023, and these could affect IPD epidemiology as well.^1,4

Study Design

The ongoing prospective study has monitored IPD among children at participating hospitals since 1993. It included individuals aged younger than 18 years with culture-proven IPD.^2,5 Eight sites contributed cases from 2018 to 2025. Four sites in Denver, Orange County, St. Louis, and Seattle joined in 2025; the network now spans 12 children’s hospitals in 10 states.^1,2 Case data were collected on standardized case report forms. Available isolates were serotyped by the Quellung reaction at the Infectious Diseases Research Laboratory at Texas Children’s Hospital. The investigators used the Fisher exact test to compare the pre-PCV20 period (2018-2023) with the post-PCV20 period (2024-2025).¹

Shifts in Serotype Distribution

Among children younger than 24 months, the proportion of IPD caused by the 7 PCV20-added serotypes fell from 27.8% (63/227) in 2018-2023 to 17.9% (12/67) in 2024-2025. This difference was not statistically significant (P = .11).¹

The investigators also examined whether RSV-targeted interventions could explain the trend. Among children younger than 60 months, the decline in PCV20-added serotypes did not differ significantly between the usual RSV season and the rest of the year:¹

• Within the RSV season, the proportion fell from 24.3% to 18.9%.
• Outside the RSV season, it fell from 26.2% to 12.1%.

The proportion of cases caused by serotypes 3 and 19F rose as the PCV20-added serotypes declined. Both serotypes are covered by PCV13.² The investigators also saw declines in serotypes 15A and 15C, but not 15B.² Preliminary data from January to June 2026 showed the same pattern. Among 64 cases with serotype data, 3 serotypes predominated:²

• Serotype 19F caused 18 cases (28.1%).
• Serotype 3 caused 14 cases (21.9%).
• Serotype 23B caused 9 cases (14.1%).

Changes in Patient Age and Clinical Presentation

The investigators identified 968 cases from 2018 to 2025: 669 in 2018-2023 and 299 in 2024-2025. Overall, 85.7% of children had received at least 1 PCV dose, and 52.7% had an underlying condition. Children aged 59 months or younger made up a smaller share of cases in the later period (63.4% vs 50.8%; P < .0001).²

Clinical presentations also shifted:²

• Bacteremia as a primary diagnosis declined from 36.9% to 27.8% (P = .005).
• Mastoiditis increased from 11.1% to 17.7% (P = .005).

Across 2018-2025, the most common serotype differed by presentation:²

• Serotype 3 was the most common cause of mastoiditis (29.9%) and pneumonia (28.2%).
• Serotype 35B was the most common cause of meningitis (13.0%).
• Serotype 23B was the most common cause of bacteremia (13.0%).

Antimicrobial Nonsusceptibility

From 2018 to 2025, 9.7% of isolates (91/935) were nonsusceptible to penicillin and 1.6% (14/854) were nonsusceptible to ceftriaxone. Serotypes 19A, 35B, and 23B were most often associated with penicillin nonsusceptibility. Serotypes 35B and 19A were most often associated with ceftriaxone nonsusceptibility. Among meningitis cases, 37.3% had a penicillin minimum inhibitory concentration greater than 0.06 µg/mL. For ceftriaxone, 9.0% had a minimum inhibitory concentration greater than 0.5 µg/mL.

Limitations and Next Steps

The investigators cautioned that the data may not reflect national trends because the network consists of large children’s hospitals in metropolitan areas in 10 states. The study is funded through a collaboration with Pfizer, with Baylor College of Medicine as sponsor, and some coauthors are Pfizer employees. Surveillance is ongoing.^1,2

REFERENCES

1. Kaplan S, Barson W, Lin P, et al. Early Trends for Invasive Pneumococcal Disease in Children After the Introduction of the 20-valent Pneumococcal Conjugate Vaccine. Presented at: IDWeek 2026; October 21–October 24; Washington, D.C.

2. Hultén K. Early trends for invasive pneumococcal disease in children after the introduction of the 20-valent pneumococcal conjugate vaccine. Presented at: IDWeek 2026; October 22, 2026; Washington, D.C.

3. ACIP updates: recommendations for use of 20-valent pneumococcal conjugate vaccine in children—United States, 2023. MMWR Morb Mortal Wkly Rep. 2023;72(39):1072. doi:10.15585/mmwr.mm7239a5

4. Jones JM, Fleming-Dutra KE, Prill MM, et al. Use of nirsevimab for the prevention of respiratory syncytial virus disease among infants and young children: Recommendations of the Advisory Committee on Immunization Practices — United States, 2023. Morb Mortal Wkly Rep. 2023;72:920–925. doi:10.15585/mmwr.mm7234a4

5. Kaplan SL, Barson WJ, Ling Lin P, et al. Invasive pneumococcal disease at eight children's hospitals in the United States, 2018-2023. Pediatr Infect Dis J. 2026;45(4):300-306. doi:10.1097/INF.0000000000005039