Pneumococcal VaccinesPhase 1/2NCT06151288

Safety, Tolerability, and Immunogenicity Study of a 31-Valent Pneumococcal Conjugate Vaccine (VAX-31) in Adults

A Phase 1/2 study testing 31 valent pneumococcal conjugate vaccine and 20 valent pneumococcal conjugate vaccine in people with Pneumococcal Vaccines, run by Vaxcyte, Inc. at 25 sites in United States.

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record

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Trial summary

Who is it for?: Ages 50 years and olderHealthy volunteers can take part
Conditions the study is for: Pneumococcal Vaccines
What is being tested?: 31 valent pneumococcal conjugate vaccine and 20 valent pneumococcal conjugate vaccine
Type of treatment: Vaccines, Injection or infusion
Could I receive a placebo?: No, everyone receives an active treatment
How many people: 1,015 participants
Where: 25 sitesUnited States
Study dates: 8 Nov 2023to 17 Jul 2024
Phase: Phase 1/2
Are there results?: Yes, posted in the registrySummary in the doctors' view

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

Ages 50 years and older
All sexes
Healthy volunteers accepted
Adult, Older adult

Who may be able to join

Male or female aged 50 to 64 years (inclusive) for Stage 1, or 50 years and older (inclusive) for Stage 2 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 at 6 months after the study vaccination.
In good general health as determined by medical history, vital signs, physical examination, and clinical judgment of the Investigator.
Willing to have blood samples collected, stored indefinitely, and used for research purposes.
Able to provide proof of identity to the satisfaction of the study staff completing the enrollment process.
Women 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
Able to access and use a smartphone, tablet, computer, or other device connected to Wi-Fi or cellular network for completion of an electronic diary.

Who cannot join

Previous pneumococcal disease (either confirmed or self-reported).
Previous receipt of a licensed or investigational pneumococcal vaccine.
Receipt of any investigational study product within 30 days prior to enrollment into the study, currently participating in another interventional investigational study, or having plans to receive another investigational product(s) while on study.
Planned or actual administration of any licensed vaccine during the period starting 30 days before enrollment into the study through Month 1.
Physical examination indicating any clinically significant medical condition.
Body Temperature >38.0°C (>100.4°F) or acute illness within 3 days prior to study vaccination (subject may be rescheduled).

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Previous or existing diagnosis of HIV, Hepatitis B, or Hepatitis C.
History of severe allergic reaction with generalized urticaria, angioedema, or anaphylaxis.
Female who is pregnant, breastfeeding, or planning to become pregnant during study participation.
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.
Any other chronic or clinically significant medical condition that, in the opinion of the Investigator, would jeopardize the safety or rights of the subject or confound evaluation of the study vaccine.
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.
Received blood or blood product (including Immune Globulin IV) within 90 days prior to enrollment into the study.
Received systemic corticosteroids (except for inhaled, topical, intra-articular) for
≥14 consecutive days and has not completed treatment ≤30 days prior to enrollment into the study.
Receiving immunosuppressive therapy.
History of malignancy ≤5 years before enrollment, except for adequately treated basal cell or squamous cell skin cancer or in situ cervical cancer

Trial locations and contacts

25 sites in 1 country.

City, postcode or hospital

25 sites in 1 country

United States25 sites

Charlottesville Medical Research
Charlottesville, Virginia, 22911
CTI Clinical Research Center
Cincinnati, Ohio, 45212
Velocity Clinical Research, Cleveland
Cleveland, Ohio, 44122
DM Clinical Research - Detroit
Detroit, Michigan, 48076
Healthcare Research Network II, LLC
Flossmoor, Illinois, 60422
Benchmark Research
Fort Worth, Texas, 76135
Research Centers of America
Hollywood, Florida, 33024
Health Awareness
Jupiter, Florida, 33458
AMR Knoxville
Knoxville, Tennessee, 37909
WR-CRCN
Las Vegas, Nevada, 89106
Johnson County Clin-Trials
Lenexa, Kansas, 66219
Optimal Research
Melbourne, Florida, 32934
AMR Mobile
Mobile, Alabama, 36608
Health Research of Hampton Roads
Newport News, Virginia, 23606
Coastal Carolina Research
North Charleston, South Carolina, 29405
Velocity Clinical Research Omaha
Omaha, Nebraska, 68134
DM Clinical Research - Philadelphia
Philadelphia, Pennsylvania, 19107
AMR Phoenix
Phoenix, Arizona, 85282
Rochester Clinical Research
Rochester, New York, 14609
CenExel JBR Clinical Research
Salt Lake City, Utah, 84107
Benchmark Research
San Angelo, Texas, 76904
Velocity Clinical Research, Savannah
Savannah, Georgia, 31406
Precision Clinical Research
Sunrise, Florida, 33351
Cenexel AMRI
Toms River, New Jersey, 08755
Velocity Clinical Research
Warwick, Rhode Island, 02886

Other trials in United States

About this study

Official title: A Phase 1/2, Randomized, Observer-Blind, Dose-Finding, Active-Controlled, Parallel-Group, Clinical Study to Evaluate the Safety, Tolerability, and Immunogenicity of a 31-Valent Pneumococcal Conjugate Vaccine (VAX-31) in Healthy Adults Aged 50 Years and Older

The objective of the study is to evaluate the safety, tolerability and immunogenicity of a single injection of VAX-31 at 3 dose levels compared to Prevnar 20™ (PCV20) in adults 50 to 64 years of age in Stage 1. Stage 2 will evaluate the safety, tolerability, and immunogenicity of a single injection of VAX-31 at 3 dose levels compared to PCV20 in adults aged 50 years and older.

Conditions: Pneumococcal Vaccines
Being tested: 31 valent pneumococcal conjugate vaccine, 20 valent pneumococcal conjugate vaccine

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

31 valent pneumococcal conjugate vaccineBiological
0.5 ml dose of VAX-31 was administered into the deltoid muscle at Day 1
20 valent pneumococcal conjugate vaccineBiological
Also called PCV20, Prevnar 20™
0.5 ml dose of PCV20 was administered into the deltoid muscle at Day 1

Study groups in NCT06151288
Study group	Role	What they receive
Group 1	Experimental	Participants received a single low dose of VAX-31 administered as an intramuscular injection at Day 1. 1.1 mcg for all serotypes with the exception of serotypes 1, 5, and 22F which is 1.65 mcg. Receives: Biological: 31 valent pneumococcal conjugate vaccine
Group 2	Experimental	Participants received a single mid dose of VAX-31 administered as an intramuscular injection at Day 1. 2.2 mcg for all serotypes with the exception of serotypes 1, 5, and 22F which is 3.3 mcg. Receives: Biological: 31 valent pneumococcal conjugate vaccine
Group 3	Experimental	Participants received a single high dose of VAX-31 administered as an intramuscular injection at Day 1. 3.3 mcg for all serotypes with the exception of serotypes 1, 5, and 22F which is 4.4 mcg. Receives: Biological: 31 valent pneumococcal conjugate vaccine
Group 4	Active comparator	Participants received a single intramuscular injection of the standard dose of PCV20 at Day 1. Receives: Biological: 20 valent pneumococcal conjugate vaccine

What is being measured

The primary outcome is the main question the study is designed to answer.

Percentage of Subjects Reporting Solicited Local Reactions Within 7 Days After Vaccination (Redness, Swelling, and Pain at Injection Site) in Each Age Group
Solicited local reactions include redness/erythema, swelling/induration, and pain at injection site within 7 days after vaccination in each age group.
Measured: 7 days after vaccination
Percentage of Subjects Reporting Solicited Systemic Events Within 7 Days After Vaccination (Fever, Headache, Fatigue, Muscle Pain, and Joint Pain) in Each Age Group Vaccination in Each Age Group
Solicited systemic reactions include fever, headache, fatigue, muscle pain, and joint pain.
Measured: 7 days after vaccination
Percentage of Subjects Reporting Unsolicited Adverse Event in Each Age Group
Percentage of participants in each age group with adverse events (AEs) whose date of onset occurs after the study vaccine and within the 1 month after vaccination.
Measured: 1 month after vaccination
Percentage of Subjects Reporting Serious Adverse Event
Percentage of participants with SAEs.
Measured: 6 months after vaccination
Percentage of Subjects Reporting New Onset of Chronic Illness
Percentage of participants with NOCIs
Measured: 6 months after vaccination
Percentage of Subjects Reporting Medically Attended Adverse Event
Percentage of participants with MAAEs.
Measured: 6 months after vaccination

Secondary outcomes (4)

Percentage of Subjects With Adverse Events Due to Clinically Significant Laboratory Values
Laboratory values that resulted in treatment and reporting as adverse events 1 month following vaccination.
Measured: 1 month after vaccination
Percentage of Participants With a Shift From Normal at Baseline to Abnormal at Post-vaccination in Safety Laboratory Parameters (Hematology, Clinical Chemistry, Urinalysis)
Shifts from Normal at Baseline to Abnormal on Month 1 (30 days after vaccination) in Hematology, Clinical Chemistry and Urinalysis Parameters Occurring in Subjects Aged 50+ Years.
Measured: 1 month after vaccination
31 VAX-31 Pneumococcal Serotype-specific OPA Geometric Mean Titer
Antibody geometric mean titers as measured by OPA for the 31 pneumococcal serotypes in VAX-31.
Measured: 1 month after vaccination
31 VAX-31 Pneumococcal Serotype-specific IgG Geometric Mean Concentration
Antibody geometric mean concentrations as measured by IgG for the 31 pneumococcal serotypes in VAX-31.
Measured: 1 month after vaccination

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

8 Nov 202317 Jul 2024

First posted30 Nov 2023
Study start8 Nov 2023
Primary completion17 Jul 2024
Study completion17 Jul 2024

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Posted resultsParticipant flow, outcome measures and adverse events reported by the sponsor.
Publications (1)Papers the sponsor has linked to this study.
Other trials for Pneumococcal VaccinesStudies of the same condition, open and under way.
What the trial phases meanHow a treatment moves from first tests in people to approval.

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design

Study type: Interventional
Phase: Phase 1/2
Primary purpose: Prevention
Allocation: Randomised
Intervention model: Parallel groups
Masking: Quadruple blind
Who is masked: Participant, Care provider, Investigator, Outcomes assessor
Enrolment: 1,015 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT06151288
Sponsor's protocol ID: VAX31-101
Status last verified: Jul 2025
First submitted: 10 Nov 2023
Last updated: 28 Jul 2025
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: Yes
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: Yes: 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.

Publications

Wassil J, Fairman J, Fierro CA, Clark J, Bennett S, Johnson D, Jiang Q, Migone TS, Paschenko A, Simon JK, Lamola S, Sisti M. Safety, tolerability, and immunogenicity of a 31-valent pneumococcal conjugate vaccine (VAX-31) in healthy adults aged 50 years and older from the USA: a phase 1/2, double-blinded, active-controlled, parallel-group, dose-finding randomised clinical trial. Lancet Infect Dis. 2026 Jul;26(7):739-750. doi: 10.1016/S1473-3099(26)00059-9. Epub 2026 Mar 18.
PubMed 41864214

Want to know more?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

See locations

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Active, not recruitingObservational study
A Study to Learn About the Safety of PREVENAR 20 Vaccine in Infants Aged Between Two to Six Months
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Active, not recruitingPhase 3
A Clinical Study to Evaluate the Safety, Tolerability, and Immunogenicity of VAX-31 With Influenza Vaccine in Adults ≥ 50 Years of Age
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All Pneumococcal Vaccines trials

Study at a glance

From the registry record, last updated by the sponsor on 28 Jul 2025. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: A Phase 1/2, Randomized, Observer-Blind, Dose-Finding, Active-Controlled, Parallel-Group, Clinical Study to Evaluate the Safety, Tolerability, and Immunogenicity of a 31-Valent Pneumococcal Conjugate Vaccine (VAX-31) in Healthy Adults Aged 50 Years and Older
ClinicalTrials.gov ID: NCT06151288
Acronym / sponsor ID: VAX31-101
Conditions: Pneumococcal Vaccines
Phase: Phase 1/2
Study type: Interventional
Recruitment status: Completed
Enrolment: 1,015 participants (actual)
Lead sponsor: Vaxcyte, Inc.Industry (pharma, biotech, devices)
Study start: 8 Nov 2023 (actual)
Primary completion: 17 Jul 2024 (actual)
Study completion: 17 Jul 2024 (actual)
First posted: 30 Nov 2023 (actual)
Results: Posted 28 Jul 2025

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

Study design

Primary purpose: Prevention
Allocation: Randomised
Intervention model: Parallel groups
Masking: Quadruple blind (participant, care provider, investigator, outcomes assessor)
Number of arms: 4

Arm	Type	Receives
Group 1	Experimental	Biological: 31 valent pneumococcal conjugate vaccineParticipants received a single low dose of VAX-31 administered as an intramuscular injection at Day 1. 1.1 mcg for all serotypes with the exception of serotypes 1, 5, and 22F which is 1.65 mcg.
Group 2	Experimental	Biological: 31 valent pneumococcal conjugate vaccineParticipants received a single mid dose of VAX-31 administered as an intramuscular injection at Day 1. 2.2 mcg for all serotypes with the exception of serotypes 1, 5, and 22F which is 3.3 mcg.
Group 3	Experimental	Biological: 31 valent pneumococcal conjugate vaccineParticipants received a single high dose of VAX-31 administered as an intramuscular injection at Day 1. 3.3 mcg for all serotypes with the exception of serotypes 1, 5, and 22F which is 4.4 mcg.
Group 4	Active comparator	Biological: 20 valent pneumococcal conjugate vaccineParticipants received a single intramuscular injection of the standard dose of PCV20 at Day 1.

Who may qualify

Ages: 50 years and older
Sex: All
Healthy volunteers: Accepted
Age groups: Adult, Older adult

Key inclusion criteria (8 listed)

Male or female aged 50 to 64 years (inclusive) for Stage 1, or 50 years and older (inclusive) for Stage 2 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 at 6 months after the study vaccination.
In good general health as determined by medical history, vital signs, physical examination, and clinical judgment of the Investigator.
Willing to have blood samples collected, stored indefinitely, and used for research purposes.

Key exclusion criteria (17 listed)

Previous pneumococcal disease (either confirmed or self-reported).
Previous receipt of a licensed or investigational pneumococcal vaccine.
Receipt of any investigational study product within 30 days prior to enrollment into the study, currently participating in another interventional investigational study, or having plans to receive another investigational product(s) while on study.
Planned or actual administration of any licensed vaccine during the period starting 30 days before enrollment into the study through Month 1.
Physical examination indicating any clinically significant medical condition.

Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.

Interventions

Intervention	Type	Arms
31 valent pneumococcal conjugate vaccine0.5 ml dose of VAX-31 was administered into the deltoid muscle at Day 1	Biological	Group 1, Group 2, Group 3
20 valent pneumococcal conjugate vaccineAlso: PCV20, Prevnar 20™0.5 ml dose of PCV20 was administered into the deltoid muscle at Day 1	Biological	Group 4

Primary outcome

Percentage of Subjects Reporting Solicited Local Reactions Within 7 Days After Vaccination (Redness, Swelling, and Pain at Injection Site) in Each Age Group
Time frame: 7 days after vaccination
Solicited local reactions include redness/erythema, swelling/induration, and pain at injection site within 7 days after vaccination in each age group.
Percentage of Subjects Reporting Solicited Systemic Events Within 7 Days After Vaccination (Fever, Headache, Fatigue, Muscle Pain, and Joint Pain) in Each Age Group Vaccination in Each Age Group
Time frame: 7 days after vaccination
Solicited systemic reactions include fever, headache, fatigue, muscle pain, and joint pain.
Percentage of Subjects Reporting Unsolicited Adverse Event in Each Age Group
Time frame: 1 month after vaccination
Percentage of participants in each age group with adverse events (AEs) whose date of onset occurs after the study vaccine and within the 1 month after vaccination.
Percentage of Subjects Reporting Serious Adverse Event
Time frame: 6 months after vaccination
Percentage of participants with SAEs.
Percentage of Subjects Reporting New Onset of Chronic Illness
Time frame: 6 months after vaccination
Percentage of participants with NOCIs
Percentage of Subjects Reporting Medically Attended Adverse Event
Time frame: 6 months after vaccination
Percentage of participants with MAAEs.

4 secondary outcomes

Percentage of Subjects With Adverse Events Due to Clinically Significant Laboratory Values
Time frame: 1 month after vaccination
Percentage of Participants With a Shift From Normal at Baseline to Abnormal at Post-vaccination in Safety Laboratory Parameters (Hematology, Clinical Chemistry, Urinalysis)
Time frame: 1 month after vaccination
31 VAX-31 Pneumococcal Serotype-specific OPA Geometric Mean Titer
Time frame: 1 month after vaccination
31 VAX-31 Pneumococcal Serotype-specific IgG Geometric Mean Concentration
Time frame: 1 month after vaccination

Results and safety

Results posted to the registry on 28 Jul 2025, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
VAX-31 Low Dose	255	247
VAX-31 Mid Dose	254	247
VAX-31 High Dose	253	248
PCV20	253	249

Primary outcome: Percentage of Subjects Reporting Solicited Local Reactions Within 7 Days After Vaccination (Redness, Swelling, and Pain at Injection Site) in Each Age Group

Time frame: 7 days after vaccination. Number. Unit: percentage of participants

Measure	VAX-31 Low Dose Overall (Age 50+) n = 253	VAX-31 Mid Dose Overall (Age 50+) n = 254	VAX-31 High Dose Overall (Age 50+) n = 253	PCV20 Overall (Age 50+) n = 252	VAX-31 Low Dose Age 50-59 Years n = 145	VAX-31 Mid Dose Age 50-59 Years n = 144	VAX-31 High Dose Age 50-59 Years n = 140	PCV20 Age 50-59 Years n = 116	VAX-31 Low Dose Age 60+ Years n = 108	VAX-31 Mid Dose Age 60+ Years n = 110	VAX-31 High Dose Age 60+ Years n = 113	PCV20 Age 60+ Years n = 136	VAX-31 Low Dose Age 65+ Years n = 58	VAX-31 Mid Dose Age 65+ Years n = 59	VAX-31 High Dose Age 65+ Years n = 53	PCV20 Age 65+ Years n = 67
Any solicited local AE; Overall, Any Grade	66.8	67.7	74.3	60.3	72.4	75.0	76.4	68.1	59.3	58.2	71.7	53.7	63.8	49.2	67.9	44.8
Pain at injection site; Overall, Any Grade	66.0	66.9	73.5	59.9	71.7	73.6	75.0	68.1	58.3	58.2	71.7	52.9	62.1	49.2	67.9	43.3
Erythema (redness) at injection site; Overall, Any Grade	6.3	7.5	7.1	4.4	7.6	10.4	7.1	5.2	4.6	3.6	7.1	3.7	1.7	1.7	3.8	3.0
Edema (swelling) at injection site; Overall, Any Grade	5.5	7.9	7.1	3.6	6.9	7.6	7.1	5.2	3.7	8.2	7.1	2.2	1.7	5.1	5.7	0

Population analysed: Safety population, defined as all subjects who received study vaccine and provided safety assessment data. Subject safety data were analyzed according to the vaccine as received.

Primary outcome: Percentage of Subjects Reporting Solicited Systemic Events Within 7 Days After Vaccination (Fever, Headache, Fatigue, Muscle Pain, and Joint Pain) in Each Age Group Vaccination in Each Age Group

Time frame: 7 days after vaccination. Number. Unit: percentage of participants

Measure	VAX-31 Low Dose Overall (Age 50+) n = 253	VAX-31 Mid Dose Overall (Age 50+) n = 254	VAX-31 High Dose Overall (Age 50+) n = 253	PCV20 Overall (Age 50+) n = 252	VAX-31 Low Dose Age 50-59 Years n = 145	VAX-31 Mid Dose Age 50-59 Years n = 144	VAX-31 High Dose Age 50-59 Years n = 140	PCV20 Age 50-59 Years n = 116	VAX-31 Low Dose Age 60+ Years n = 108	VAX-31 Mid Dose Age 60+ Years n = 110	VAX-31 High Dose Age 60+ Years n = 113	PCV20 Age 60+ Years n = 136	VAX-31 Low Dose Age 65+ Years n = 58	VAX-31 Mid Dose Age 65+ Years n = 59	VAX-31 High Dose Age 65+ Years n = 53	PCV20 Age 65+ Years n = 67
Any solicited systemic AE (any grade)	58.5	61.4	68.0	57.1	64.1	65.3	71.4	59.5	50.9	56.4	63.7	55.1	50.0	54.2	60.4	55.2
Fever (any grade)	1.2	1.2	1.6	0.8	1.4	1.4	2.1	0.9	0.9	0.9	0.9	0.7	1.7	1.7	0.0	0.0
Fatigue (any grade)	36.8	36.2	46.2	38.9	40.0	40.3	49.3	37.1	32.4	30.9

Primary outcome: Percentage of Subjects Reporting Unsolicited Adverse Event in Each Age Group

Time frame: 1 month after vaccination. Number. Unit: percentage of participants

Measure	VAX-31 Low Dose Overall (Age 50+) n = 255	VAX-31 Mid Dose Overall (Age 50+) n = 254	VAX-31 High Dose Overall (Age 50+) n = 253	PCV20 Overall (Age 50+) n = 253	VAX-31 Low Dose Age 50-59 Years n = 147	VAX-31 Mid Dose Age 50-59 Years n = 144	VAX-31 High Dose Age 50-59 Years n = 140	PCV20 Age 50-59 Years n = 116	VAX-31 Low Dose Age 60+ Years n = 108	VAX-31 Mid Dose Age 60+ Years n = 110	VAX-31 High Dose Age 60+ Years n = 113	PCV20 Age 60+ Years n = 137	VAX-31 Low Dose Age 65+ Years n = 58	VAX-31 Mid Dose Age 65+ Years n = 59	VAX-31 High Dose Age 65+ Years n = 53	PCV20 Age 65+ Years n = 67
Value	16.5	16.9	18.6	16.6	18.4	16.7	22.9	18.1	13.9	17.3	13.3	15.3	17.2	18.6	13.2	14.9

Population analysed: Safety population, defined as all subjects who received study vaccine. Subject safety data were analyzed according to the vaccine they received.

Primary outcome: Percentage of Subjects Reporting Serious Adverse Event

Time frame: 6 months after vaccination. Number. Unit: percentage of participants

Measure	VAX-31 Low Dose Overall (Age 50+) n = 255	VAX-31 Mid Dose Overall (Age 50+) n = 254	VAX-31 High Dose Overall (Age 50+) n = 253	PCV20 Overall (Age 50+) n = 253	VAX-31 Low Dose Age 50-59 Years n = 147	VAX-31 Mid Dose Age 50-59 Years n = 144	VAX-31 High Dose Age 50-59 Years n = 140	PCV20 Age 50-59 Years n = 116	VAX-31 Low Dose Age 60+ Years n = 108	VAX-31 Mid Dose Age 60+ Years n = 110	VAX-31 High Dose Age 60+ Years n = 113	PCV20 Age 60+ Years n = 137	VAX-31 Low Dose Age 65+ Years n = 58	VAX-31 Mid Dose Age 65+ Years n = 59	VAX-31 High Dose Age 65+ Years n = 53	PCV20 Age 65+ Years n = 67
Value	0.8	1.2	2.0	1.2	1.4	0.7	2.1	0.0	0.0	1.8	1.8	2.2	0.0	1.7	3.8	3.0

Population analysed: Safety population, defined as all subjects who received study vaccine. Subject safety data were analyzed according to the vaccine they received.

4 secondary outcomes are reported in the full results.

Adverse events

Time frame: 6 months. Other adverse events reported at 1% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
VAX-31 Low Dose Overall (Age 50+)	2 of 255 (0.8%)	189 of 255 (74.1%)	0 of 255
VAX-31 Mid Dose Overall (Age 50+)	3 of 254 (1.2%)	196 of 254 (77.2%)	0 of 254
VAX-31 High Dose Overall (Age 50+)	5 of 253 (2%)	209 of 253 (82.6%)	0 of 253
PCV20 Overall (Age 50+)	3 of 253 (1.2%)	178 of 253 (70.4%)	0 of 253

Limitations and caveats (from the sponsor): Some limitations of this clinical study include the lack of a group, such as 3.3 mcg or 4.4 mcg, for all serotypes, aimed at understanding whether the dose response of polysaccharide can overcome carrier suppression. The relatively low ethnic diversity of participants is also a limitation, which will be addressed in larger phase 3 clinical trials.

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 28 Jul 2025.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 41864214Wassil J, Fairman J, Fierro CA, Clark J, Bennett S, Johnson D, Jiang Q, Migone TS, Paschenko A, Simon JK, Lamola S, Sisti M. Safety, tolerability, and immunogenicity of a 31-valent pneumococcal conjugate vaccine (VAX-31) in healthy adults aged 50 years and older from the USA: a phase 1/2, double-blinded, active-controlled, parallel-group, dose-finding randomised clinical trial. Lancet Infect Dis. 2026 Jul;26(7):739-750. doi: 10.1016/S1473-3099(26)00059-9. Epub 2026 Mar 18.
Individual participant dataSharing planned: Yes. 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.

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Referral and contact

AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.

Clinical Development study director

Vaxcyte, Inc.

25 sites in 1 country: see every site and its status.

Questions about this trial

What is this clinical trial studying?

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 8 inclusion and 17 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 28 Jul 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 25 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

What does this combined phase mean?

Phase 1 studies test a treatment in a small group of people for the first time or in a new way, mainly to check safety and find the right dose.

Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.

Not every study follows the same path, and some studies (observational studies, device studies) have no phase.

Are results available for this study?

Yes. Results are posted in the registry (first posted 28 Jul 2025). A summary is in the For doctors view, and the full results are on ClinicalTrials.gov.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Percentage of Subjects Reporting Solicited Local Reactions Within 7 Days After Vaccination (Redness, Swelling, and Pain at Injection Site) in Each Age Group (time frame: 7 days after vaccination). The study lists 6 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT06151288, which also lists 1 linked publication.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 28 Jul 2025.