Safety, Tolerability, and Immunogenicity of VAX-31 in Adults ≥50 Years With Immunobridging to Adults 18-49

May 12, 2026 updated by: Vaxcyte, Inc.

A Phase 3, Randomized, Double-Blind, Active-Controlled Clinical Study to Evaluate the Safety, Tolerability, and Immunogenicity of VAX-31 in Healthy Subjects 50 Years of Age and Older With Immunobridging to Subjects 18-49 Years of Age

The primary objectives of this study are to evaluate the safety, tolerability, immunologic noninferiority (for shared serotypes) and immunologic superiority (for novel serotypes) of VAX-31 compared to PCV21 and PCV20 in adults ≥50 years of age, and to bridge the immune responses induced by VAX-31 in adults 50-64 years of age to adults 18-49 years of age.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Active, not recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Actual)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
4049

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • United States
    • Alabama
      • Birmingham, Alabama, United States, 35216
        • Accel Research Site - Achieve - Birmingham - ERN
    • Arizona
      • Chinle, Arizona, United States, 86503
        • Center for Indigenous Health - Chinle - Johns Hopkins Project
      • Whiteriver, Arizona, United States, 85941
        • Center for Indigineous Health - Whiteriver - John Hopkins Project
    • California
      • Riverside, California, United States, 92506
        • Clinical Innovations Trials - Riverside - CenExel
    • Florida
      • Hollywood, Florida, United States, 33024
        • Research Centers of America - Hollywood - CenExel
      • Jupiter, Florida, United States, 33458
        • Health Awareness - Jupiter - ERN
      • Miami, Florida, United States, 33135
        • Suncoast Research Group LLC
      • Sunrise, Florida, United States, 33351
        • Precision Clinical Research - Sunrise
    • Georgia
      • Stockbridge, Georgia, United States, 30281
        • Clinical Research Atlanta - Headlands
    • Indiana
      • Valparaiso, Indiana, United States, 46383
        • Velocity Clinical Research - Valparaiso (Buynak Clinical Research)
    • Kansas
      • Lenexa, Kansas, United States, 66219
        • Johnson County Clin-Trials - JCCT
      • Wichita, Kansas, United States, 67207
        • Alliance for Multispecialty Research, LLC - West Wichita
    • Louisiana
      • New Orleans, Louisiana, United States, 70115
        • DelRicht Clinical Research, LLC - New Orleans
    • Michigan
      • Southfield, Michigan, United States, 48034
        • Headlands Research - Detroit - Headlands
    • Mississippi
      • Gulfport, Mississippi, United States, 39503
        • DelRicht Research, LLC - Gulfport
      • Ridgeland, Mississippi, United States, 39157
        • Sky Integrative Medical Center - SKYCRNG
    • Missouri
      • Kansas City, Missouri, United States, 64114
        • Alliance for Multispecialty Research, LLC - Kansas City
    • Nebraska
      • Omaha, Nebraska, United States, 68134
        • Velocity Clinical Research
    • New Jersey
      • Toms River, New Jersey, United States, 08755
        • Advanced Memory Research Institute - CenExe
    • New Mexico
      • Gallup, New Mexico, United States, 87301
        • Center for Indigineous Health - Gallup - John Hopkins Project
      • Shiprock, New Mexico, United States, 87420
        • Center for Indigineous Health - Shiprock - John Hopkins Project
    • New York
      • Rochester, New York, United States, 14609
        • Rochester Clinical Research - ATLAS - Rochester
    • Ohio
      • Cincinnati, Ohio, United States, 45212
        • CTI Clinical Research Center
    • Oklahoma
      • Norman, Oklahoma, United States, 73072
        • Lynn Institute of Norman
    • Pennsylvania
      • Philadelphia, Pennsylvania, United States, 19107
        • DM Clinical Research - Philadelphia
    • South Carolina
      • North Charleston, South Carolina, United States, 29405
        • Coastal Carolina Research Center - Alcanza - HyperCore
    • Texas
      • San Antonio, Texas, United States, 78229
        • Flourish Research - San Antonio
      • Sugar Land, Texas, United States, 77478
        • DM Clinical Research - Sugarland
    • Utah
      • Salt Lake City, Utah, United States, 84107
        • JBR Clinical Research - CenExel JBR
    • Virginia
      • Charlottesville, Virginia, United States, 22911
        • Charlottesville Medical Research Center - Alcanza - HyperCore

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria:

  • Male or female ≥18 years of age (inclusive) at the time of randomization into the study.
  • Able and willing to complete the informed consent process.
  • Available for clinical follow-up through the last study visit.
  • In good general health or with stable underlying chronic condition(s), as determined by medical history, oral temperature, physical examination, and clinical judgment of the Investigator (ongoing chronic conditions must be documented as stable per Investigator).
  • Willing to have blood samples collected and used for research purposes.
  • Able to provide proof of identity to the satisfaction of the site personnel completing the enrollment process.
  • Female participants of childbearing potential, defined as premenopausal females capable of becoming pregnant, must have a negative urine pregnancy test immediately prior to randomization and agree to use acceptable contraception. Male subjects with partners of childbearing potential must agree to practice an acceptable contraception method.
  • Able to access and use a device connected to Wi-Fi or cellular network for completion of an electronic diary (eDiary).

Exclusion Criteria:

  • History of invasive pneumococcal disease (IPD) or pneumococcal pneumonia (either confirmed or self-reported) at any age.
  • Previous receipt of any licensed or investigational pneumococcal vaccine at any age.
  • Receipt of any investigational product within 30 days prior to Day 1, currently participating in another interventional investigational study, or having plans to receive another investigational product(s) while on study.
  • Receipt of any live vaccine within 30 days prior to Day 1, or receipt of any non-live (including inactivated) vaccine within 14 days prior to Day 1.
  • Body temperature >38.0°C (>100.4°F) or acute illness within 3 days prior to study vaccination (subject may be rescreened).
  • Current diagnosis of human immunodeficiency virus, Hepatitis B, or Hepatitis C.
  • History of severe allergic reaction with generalized urticaria, angioedema, or anaphylaxis to any previous vaccination.
  • Individual who is pregnant, breastfeeding, or planning to become pregnant during study participation.
  • Has a known or suspected immunocompromising condition, including, but not limited to, leukemia, lymphoma, chronic renal failure, or congenital or acquired immunodeficiency.
  • Bleeding disorder diagnosed by a doctor (e.g., factor deficiency, coagulopathy, or platelet disorder requiring special precautions) resulting in clinically significant bruising or bleeding difficulties with IM injections or blood draws.
  • Receipt of blood or blood product (including polyclonal intravenous immunoglobulin) within 60 days prior to enrollment into the study.
  • Is currently receiving immunosuppressive or immune-modifying therapy, including systemic corticosteroids (this includes ≥3 months of prednisone equivalent from 5 to <10 mg/day and ≥2 weeks of prednisone equivalent ≥10 mg/day).
  • Received any part of a ≥14-day course of systemic corticosteroids (prednisone equivalent >10 mg/day) within 14 days of study vaccination.
  • History of malignancy ≤5 years before enrollment, except for adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer.
  • Any medical, psychiatric, or social condition that in the judgment of the Investigator is a contraindication to protocol participation or impairs a subject's ability to give informed consent.
  • Employee of, or first-degree relative of, any person employed by the Sponsor, the contract research organization (CRO), the Investigator, site personnel, or site.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

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

Arms and Interventions

Participant Group / Arm

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: Cohort 1 (VAX-31), participant ≥ 50 years of age
Participants will receive a single dose of VAX-31 administered via intramuscular injection at Day 1
Biological: 31 valent pneumococcal conjugate vaccine
0.5 mL of VAX-31 will be administered into the deltoid muscle
Active Comparator: Cohort 1 (PCV21), participant ≥ 50 years of age
Participants will receive a single dose of PCV21 (Capvaxive) administered via intramuscular injection at Day 1
Biological: PCV21
0.5 mL of the 21 valent pneumococcal conjugate vaccine will be administered into the deltoid muscle
Other Names:
  • Capvaxive
Active Comparator: Cohort 1 (PCV20), participant ≥ 50 years of age
Participants will receive a single dose of PCV20 (Prevnar 20) administered via intramuscular injection at Day 1
Biological: PCV20
0.5 mL of the 20 valent pneumococcal conjugate vaccine will be administered into the deltoid muscle
Other Names:
  • Prevnar 20
Experimental: Cohort 2 (VAX-31), participant 18-49 years of age
Participants will receive a single dose of VAX-31 administered via intramuscular injection at Day 1
Biological: 31 valent pneumococcal conjugate vaccine
0.5 mL of VAX-31 will be administered into the deltoid muscle
Active Comparator: Cohort 2 (PCV20), participant 18-49 years of age
Participants will receive a single dose of PCV20 (Prevnar 20) administered via intramuscular injection at Day 1
Biological: PCV20
0.5 mL of the 20 valent pneumococcal conjugate vaccine will be administered into the deltoid muscle
Other Names:
  • Prevnar 20

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Time Frame
Serotype-specific OPA geometric mean titers (GMT) in 50 year olds and above
Time Frame: 1 month after vaccination
1 month after vaccination
Percentage of subjects reporting solicited local adverse events (AE) (redness, swelling, and pain at injection site)
Time Frame: up to 7 days after vaccination
up to 7 days after vaccination
Percentage of subjects reporting solicited systemic AE (fever, headache, fatigue, muscle pain, and joint pain)
Time Frame: up to 7 days after vaccination
up to 7 days after vaccination
Percentage of subjects reporting unsolicited AE
Time Frame: up to 31 days after vaccination
up to 31 days after vaccination
Percentage of subjects reporting serious adverse events (SAE), new onset of chronic illness (NOCI), and medically attended adverse events (MAAE)
Time Frame: up to 6 Months after vaccination
up to 6 Months after vaccination
Serotype-specific OPA geometric mean titers (GMT) in 18 to 49 year olds and 50 to 64 year olds
Time Frame: 1 month after vaccination
1 month after vaccination

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Time Frame
Serotype-specific IgG geometric mean concentrations (GMC) in 50 year olds and above
Time Frame: 1 month after vaccination
1 month after vaccination
Serotype-specific IgG GMC in 18 to 49 year olds and 50 to 64 year olds
Time Frame: 1 month after vaccination
1 month after vaccination

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Vaxcyte, Inc.

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
December 1, 2025

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
January 1, 2027

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
January 1, 2027

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
December 8, 2025

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
December 8, 2025

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
December 16, 2025

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
May 15, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
May 12, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
May 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • VAX31-103

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

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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