Safety, Tolerability, and Immunogenicity of a 24-Valent Pneumococcal Conjugate Vaccine (VAX-24) in Healthy Infants

Randomized, Observer-Blind, Active-Controlled, Dose-Finding Study to Evaluate the Safety, Tolerability, and Immunogenicity of 24-Valent PCV (VAX-24) in Infants Given 4 Doses at 2, 4, 6, and 12-15 Months of Age With Pediatric Vaccines

The objective of the study is to evaluate the safety and tolerability of 4 injections of VAX-24 (at 3 dose levels) compared to PCV15 in infants at 2, 4, 6, and 12-15 months of age, in addition to receiving routine US concomitant vaccines. Stage 1 of the study will comprise 3 dose ascending cohorts. Stage 2 of the study will enroll the remainder of the sample size.

Study Overview

• Status: Completed
• Conditions: Pneumococcal Vaccines
• Intervention / Treatment: Biological: 0.5 ml dose of 1.1 mcg VAX-24; Biological: 0.5 ml dose of 2.2 mcg VAX-24; Biological: 0.5 ml dose of 2.2/4.4 mcg VAX-24; Biological: 0.5 ml dose of PCV20

• Study Type: Interventional
• Enrollment (Actual): 802
• Phase: Phase 2

Contacts and Locations

Study Locations

• United States
  • Arkansas
    • Jonesboro, Arkansas, United States, 72401
      • The Children's Clinic of Jonesboro, P.A.
  • California
    • Madera, California, United States, 93637
      • Madera Family Medical Group
  • Florida
    • Tampa, Florida, United States, 33617
      • Jedidiah Clinical Research
  • Kentucky
    • Bardstown, Kentucky, United States, 40004
      • Kentucky Pediatric/ Adult Research
  • Louisiana
    • Haughton, Louisiana, United States, 71037
      • ACC Pediatric Research
  • Nebraska
    • Hastings, Nebraska, United States, 68901
      • Meridian Clinical Research
    • Lincoln, Nebraska, United States, 68516
      • Midwest Children's Health Research Institute
    • Lincoln, Nebraska, United States, 68504
      • Midwest Children's Health Research Institute
    • Lincoln, Nebraska, United States, 68522
      • Midwest Children's Health Research Institute
    • Lincoln, Nebraska, United States, 68505
      • Midwest Children's Health Research Institute
  • Ohio
    • Dayton, Ohio, United States, 45414
      • Ohio Pediatric Research Assn.
  • Pennsylvania
    • Cranberry Township, Pennsylvania, United States, 16066
      • UPMC Bass Wolfson Cranberry
    • Erie, Pennsylvania, United States, 16506
      • Allegheny Health and Wellness Pavilion
    • Jefferson Hills, Pennsylvania, United States, 15025
      • UPMC Children's Community Pediatrics South Hills-Jefferson Hills
    • Pittsburgh, Pennsylvania, United States, 15217
      • UPMC Children's Community Pediatrics Bass Wolfson-Squirrel Hill
    • Pittsburgh, Pennsylvania, United States, 15234
      • UPMC Children's Community Pediatrics-Castle Shannon
    • Pittsburgh, Pennsylvania, United States, 15213
      • UPMC Primary Care Center Oakland
  • South Carolina
    • North Charleston, South Carolina, United States, 29406
      • Palmetto Pediatrics, PA
    • Simpsonville, South Carolina, United States, 29680
      • Tribe Clinical Research at Parkside Pediatrics
    • Summerville, South Carolina, United States, 29486
      • Coastal Pediatric Research
  • Tennessee
    • Kingsport, Tennessee, United States, 37660
      • Holston Medical Group
  • Texas
    • Burleson, Texas, United States, 76028
      • Ventavia Research Group
    • Houston, Texas, United States, 77065
      • Kool Kids Pediatrics
    • Houston, Texas, United States, 77087
      • Pediatric Associates
    • Houston, Texas, United States, 77008
      • Ventavia
    • Richmond, Texas, United States, 77469
      • Pediatric Center
  • Utah
    • Layton, Utah, United States, 84041
      • Alliance for Multispecialty Research
    • Murray, Utah, United States, 84107
      • Alliance for Multispecialty Research
    • Provo, Utah, United States, 84604
      • Alliance for Multispecialty Research
    • Roy, Utah, United States, 84067
      • Alliance for Multispecialty Research
    • Syracuse, Utah, United States, 84075
      • Alliance for Multispecialty Research
  • Virginia
    • Charlottesville, Virginia, United States, 22902
      • Pediatric Research of Charlottesville, LLC

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: Yes

Description

Inclusion Criteria:

1. Healthy male or female infant ≥42 days to ≤89 days (inclusive).
2. Full-term infant at least 37 weeks gestational age at birth.
3. Afebrile for ≥72 hours with a rectal temperature <38.0°C (<100.4°F) or axillary temperature <37.8°C (<100.0°F) before receipt of study vaccine.*
4. Able to attend all scheduled visits and comply with the study procedures.
5. Subject's parent/legal guardian is able to read and understands the study procedures, alternate treatments, risks and benefits, and provides written informed consent.
6. Subject's parent/legal guardian is able to fill out an ediary of solicited AE and take daily axillary temperature and measurements of local injection site reactions for the 7 days after each study vaccination.
7. Subject's parent/legal guardian has an e-mail address and access to a computer or smartphone with internet to complete the ediary.

Exclusion Criteria:

1. History of invasive pneumococcal disease (positive blood culture, positive cerebrospinal fluid culture, or other sterile site) or known history of other culture positive pneumococcal disease.
2. Previous receipt of a licensed or investigational vaccine (excluding 1 dose hepatitis B vaccine).
3. Known hypersensitivity to any vaccine.
4. Known or suspected impairment of immunological function (e.g., asplenia, HIV, primary immunodeficiency).
5. Use of any immunosuppressive therapy (Note: topical and inhaled/nebulized steroids are permitted).
6. History of failure to thrive.
7. Subject has a coagulation disorder contraindicating IM vaccination.
8. Subject or his/her mother have documented hepatitis B surface antigen-positive.
9. Has a known neurologic or cognitive behavioral disorder.
10. Has a known clinically significant congenital malformation or serious chronic disorder.
11. Receipt of a blood transfusion or blood products, including immunoglobulins.
12. Receipt of any investigational study product since birth, currently participating in another interventional investigational study, or having plans to receive another investigational product(s) while on study.
13. Any infant who cannot be adequately followed for safety according to the protocol plan.
14. Any other reason that in the opinion of the investigator may interfere with the evaluation required by the study.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Quadruple

Number of Arms

4

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: VAX-24 Low; Participants will receive 4 doses of VAX-24 administered as an intramuscular injection at 2, 4, 6, and 12-15 months of age at one of three dose levels.	Biological: 0.5 ml dose of 1.1 mcg VAX-24; 24 valent pneumococcal conjugate vaccine
Experimental: VAX-24 Mid; Participants will receive 4 doses of VAX-24 administered as an intramuscular injection at 2, 4, 6, and 12-15 months of age at one of three dose levels.	Biological: 0.5 ml dose of 2.2 mcg VAX-24; 24 valent pneumococcal conjugate vaccine
Experimental: VAX-24 Mixed; Participants will receive 4 doses of VAX-24 administered as an intramuscular injection at 2, 4, 6, and 12-15 months of age at one of three dose levels.	Biological: 0.5 ml dose of 2.2/4.4 mcg VAX-24; 24 valent pneumococcal conjugate vaccine
Active Comparator: PCV20; Participants will receive 4 doses of PCV20 administered as an intramuscular injection of the standard dose at 2, 4, 6, and 12-15 months of age.	Biological: 0.5 ml dose of PCV20; 20 valent pneumococcal conjugate vaccine

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of participants with any solicited local injection site Adverse Events (AE) within 7 days after each vaccination	Solicited local reactions include erythema, edema, and tenderness at the injection site	7 days after each vaccination
Percentage of participants with any solicited systemic AE within 7 days after each vaccination	Solicited systemic reactions include fever, irritability, decreased appetite, decreased sleep, and increased sleep	7 days after each vaccination
Percentage of participants with any related Serious Adverse Events (SAE) within 6 months after last vaccination	Percentage of participants with related SAE	6 months after last vaccination

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of subjects with any unsolicited AE within 1 month after each vaccination	Percentage of subjects with any unsolicited AE	1 month after each vaccination
Percentage of subjects with any unsolicited AE from Dose 1 through 1 month post-Dose 3	Percentage of subjects with any unsolicited AE between first and 3rd vaccination in the primary series	First vaccination (Dose 1) through 1 month after third vaccination (Dose 3)
Percentage of subjects with any AE resulting in discontinuation of study within 6 months after last vaccination	Percentage of subjects with any AE resulting in discontinuation of study	6 months after last vaccination
Percentage of subjects with any new onset of chronic illness (NOCI) within 6 months after last vaccination	Percentage of subjects with any NOCI	6 months after last vaccination
Percentage of subjects with any medically attended adverse events (MAAE) within 6 months after last vaccination	Percentage of subjects with any MAAE	6 months after last vaccination
Percentage of subjects with any SAE within 6 months after last vaccination	Percentage of subjects with any SAE	6 months after last vaccination
Percentage of subjects achieving an anti-pneumococcal Immunoglobulin G (IgG) antibody concentration ≥0.35 mcg/mL 1 month after Dose 3	Percentage of subjects achieving an anti-pneumococcal IgG antibody concentration ≥0.35 mcg/mL	1 month after Dose 3
Percentage of subjects achieving an anti-pneumococcal IgG antibody concentration ≥0.35 mcg/mL 1 month after Dose 4	Percentage of subjects achieving an anti-pneumococcal IgG antibody concentration ≥0.35 mcg/mL	1 month after Dose 4
IgG antibody Geometric Mean Concentration (GMC) 1 month after Dose 3	Antibody geometric mean concentrations as measured by IgG for the 24 pneumococcal serotypes in VAX-24	1 month after Dose 3
IgG antibody GMC 1 month after Dose 4	Antibody geometric mean concentrations as measured by IgG for the 24 pneumococcal serotypes in VAX-24	1 month after Dose 4
Opsonophagocytic activity (OPA) Geometric Mean Titer (GMT) 1 month after Dose 3	Antibody geometric mean titers s as measured by OPA for the 24 pneumococcal serotypes in VAX-24	1 month after Dose 3
OPA GMT 1 month after Dose 4	Antibody geometric mean titers s as measured by OPA for the 24 pneumococcal serotypes in VAX-24	1 month after Dose 4
IgG Geometric Mean Fold Ratio (GMFR) before Dose 4 to 1 month after Dose 4	Antibody geometric mean fold ratio as measured by IgG for the 24 pneumococcal serotypes in VAX-24	Pre-Dose 4 to 1 month after Dose 4
OPA GMFR before Dose 4 to 1 month after Dose 4	Antibody geometric mean fold rise as measured by OPA for the 24 pneumococcal serotypes in VAX-24	Pre-Dose 4 to 1 month after Dose 4
Percentage of subjects achieving at least a 4-fold increase in IgG from pre-Dose 4 to 1 month post Dose 4	Geometric mean concentration with a at least a 4-fold increase in IgG antibodies for the 24 pneumococcal serotypes in VAX-24	Pre-Dose 4 to 1 month after Dose 4
Percentage of subjects achieving at least a 4-fold increase in OPA titers from pre-Dose 4 to 1 month post Dose 4	Geometric mean titer with a at least a 4-fold increase in OPA titers for the 24 pneumococcal serotypes in VAX-24	Pre-Dose 4 to 1 month after Dose 4

Collaborators and Investigators

• Sponsor: Vaxcyte, Inc.

Study record dates

Study Major Dates

• Study Start (Actual): March 29, 2023
• Primary Completion (Actual): August 25, 2025
• Study Completion (Actual): August 25, 2025

Study Registration Dates

• First Submitted: April 24, 2023
• First Submitted That Met QC Criteria: April 24, 2023
• First Posted (Actual): May 6, 2023

Study Record Updates

• Last Update Posted (Estimated): September 11, 2025
• Last Update Submitted That Met QC Criteria: September 9, 2025
• Last Verified: September 1, 2025

More Information

Terms related to this study

• Keywords: Pneumonia; Pneumococcal Infection; 24 valent PCV
• Additional Relevant MeSH Terms: Respiratory Tract Infections; Infections; Respiratory Tract Diseases; Lung Diseases; Gram-Positive Bacterial Infections; Bacterial Infections; Bacterial Infections and Mycoses; Streptococcal Infections; Pneumonia; Pneumococcal Infections
• Other Study ID Numbers: VAX24-112

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Vaxcyte is committed to providing access to anonymized data from the company's clinical trials for the purpose of legitimate scientific research. Requests for data may be addressed to datasharing@vaxcyte.com. Requests must be accompanied by a detailed analysis plan and will be reviewed for scientific validity. Data will be made available after initial product approval. Sharing of data may require execution of a data-sharing agreement.
• IPD Sharing Time Frame: Individual participant data will be shared after deidentification and made available starting 6 months after initial product approval.
• IPD Sharing Access Criteria: Criteria will depend on the specific proposal received and may include qualification of the scientific researchers, potential contribution to the research field, scientific rigor of statistical and analytical methods, and other criteria appropriate for the proposal.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No