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VAX-31

Phase 3

Pneumococcal Vaccines | Monoclonal antibody | Infectious Disease |Vaxcyte, Inc.|Last Updated: Jun 30, 2026

Target and mechanism

ModalityMonoclonal antibody

Also known as 0.5 mL of the low dose VAX-31, of the low dose VAX-31, 0.5 mL of the mid dose VAX-31, of the mid dose VAX-31, 0.5 mL of the High-PFS dose VAX-31, of the High-PFS dose VAX-31, 31 valent pneumococcal conjugate vaccine, 31-valent pneumococcal conjugate vaccine

Success Probability

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Market & Valuation

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Trial Design

RandomizedDouble-BlindACTIVE_CONTROLLEDDMC
Total Trials5
Total Enrollment8,106

FDA Designations

BREAKTHROUGH_THERAPY

Clinical trial landscape

VAX-31 · 5 trials · 1 indication

Phase 3 3Phase 2 1Phase 1 1
NCT07425392Safety, Tolerability, and Immunogenicity of VAX-31 in Adults ≥50 Years With Prior Pneumococcal VaccinationPneumococcal Vaccines
ACTIVE NOT_RECRUITING752 Analytics
NCT07365826A Clinical Study to Evaluate the Safety, Tolerability, and Immunogenicity of VAX-31 With Influenza Vaccine in Adults ≥ 50 Years of AgePneumococcal Vaccines
ACTIVE NOT_RECRUITING1,390 Analytics
NCT07284654Safety, Tolerability, and Immunogenicity of VAX-31 in Adults ≥50 Years With Immunobridging to Adults 18-49Pneumococcal Vaccines
ACTIVE NOT_RECRUITING4,049 Analytics
PHASE3ACTIVE NOT_RECRUITING
Safety, Tolerability, and Immunogenicity of VAX-31 in Adults ≥50 Years With Prior Pneumococcal Vaccination
Pneumococcal VaccinesUnlock trial analytics
PHASE3ACTIVE NOT_RECRUITING
A Clinical Study to Evaluate the Safety, Tolerability, and Immunogenicity of VAX-31 With Influenza Vaccine in Adults ≥ 50 Years of Age
Pneumococcal VaccinesUnlock trial analytics
PHASE3ACTIVE NOT_RECRUITING
Safety, Tolerability, and Immunogenicity of VAX-31 in Adults ≥50 Years With Immunobridging to Adults 18-49
Pneumococcal VaccinesUnlock trial analytics

Study Endpoints

Primary Endpoints

Serotype-specific OPA geometric mean titers (GMT)
1 month after VAX-31 vaccination
Serotype-specific OPA geometric mean fold rise (GMFR) from baseline
1 month after VAX-31 vaccination
Percentage of subjects reporting solicited local adverse events (AE) (redness, swelling, and pain at injection site)
up to 7 days after vaccination
Percentage of subjects reporting solicited systemic AE (fever, headache, fatigue, muscle pain, and joint pain)
up to 7 days after vaccination
Percentage of subjects reporting unsolicited AE
up to 31 days after vaccination
Percentage of subjects reporting new onset of chronic illness (NOCI), medically attended AE (MAAE), and serious adverse events (SAE)
up to 6 months after vaccination
For each of the 32 serotypes (the 31 serotypes included in VAX-31, and serotype 20B), the ratio (co-administration group to sequential administration group) of opsonophagocytic activity (OPA) geometric mean titers (GMT) in evaluable participants
1 Month after VAX-31 vaccination
For each of the strains in SIV, the ratio (co-administration group to sequential administration group) of hemagglutination inhibition (HAI) GMT in evaluable participants
1 Month after SIV administration
Percentage of participants reporting solicited local adverse events (AE) within 7 days after Day 1 and Month 1 vaccination (redness, swelling, and pain at injection site) in each group
7 days after each vaccination
Percentage of participants reporting solicited systemic AE within 7 days after Day 1 and Month 1 vaccination (fever, headache, fatigue, muscle pain, and joint pain) in each group
7 days after each vaccination
Percentage of participants reporting unsolicited AE within 1 month after Day 1 and Month 1 vaccination in each group
7 days after each vaccination
Percentage of participants reporting NOCI, MAAE, and SAE within 6 months after last vaccination in each group
6 Months after last vaccination
Serotype-specific OPA geometric mean titers (GMT) in 50 year olds and above
1 month after vaccination
Percentage of subjects reporting serious adverse events (SAE), new onset of chronic illness (NOCI), and medically attended adverse events (MAAE)
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
1 month after vaccination
Percentage of subjects with any solicited local injection site adverse events (AE) within 7 days after each vaccination
7 days after each vaccination

Solicited local reactions include erythema, edema, and tenderness at the injection site

Percentage of subjects with any solicited systemic AE within 7 days after each vaccination
7 days after each vaccination

Solicited systemic reactions include fever, irritability, decreased appetite, decreased sleep, and increased sleep

Percentage of subjects with any unsolicited AE within 1 month after each vaccination
1 months after each vaccination

Percentage of subjects with unsolicited AE

Percentage of subjects with any medically attended adverse events (MAAE) within 6 months after last vaccination
6 months after last vaccination

Percentage of subjects with MAAE

Percentage of subjects with any Serious Adverse Events (SAE) within 6 months after last vaccination
6 months after last vaccination

Percentage of subjects with SAE

Percentage of subjects with any new onset of chronic illness (NOCI) within 6 months after last vaccination
6 months after last vaccination

Percentage of subjects with NOCI

Percentage of Subjects Reporting Solicited Local Reactions Within 7 Days After Vaccination (Redness, Swelling, and Pain at Injection Site) in Each Age Group
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
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
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
6 months after vaccination

Percentage of participants with SAEs.

Percentage of Subjects Reporting New Onset of Chronic Illness
6 months after vaccination

Percentage of participants with NOCIs

Percentage of Subjects Reporting Medically Attended Adverse Event
6 months after vaccination

Percentage of participants with MAAEs.

Secondary Endpoints

Serotype-specific IgG geometric mean concentration (GMC)
1 month after VAX-31 vaccination
Serotype-specific IgG geometric mean fold-rise (GMFR) from baseline
1 month after VAX-31 vaccination
For each of the 32 serotypes (the 31 serotypes included in VAX-31, and serotype 20B), the ratio (co-administration group to sequential administration group) of IgG geometric mean concentrations (GMC) in evaluable participants
1 month after VAX-31 administration
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Study Design & Arms

AllocationRANDOMIZED
MaskingQUADRUPLE
ModelPARALLEL
PurposePREVENTION

Treatment Arms

ArmTypeDescription
Cohort 1 (VAX-31): Prior PPSV23EXPERIMENTALParticipants will receive a single dose of VAX-31 administered via intramuscular injection at Day 1
Cohort 1 (PCV20): Prior PPSV23ACTIVE_COMPARATORParticipants will receive a single dose of PCV20 (Prevnar 20) administered via intramuscular injection at Day 1
Cohort 2 (VAX-31): Prior PCV20EXPERIMENTALParticipants will receive a single dose of VAX-31 administered via intramuscular injection at Day 1
Cohort 2 (PCV20): Prior PCV20ACTIVE_COMPARATORParticipants will receive a single dose of PCV20 (Prevnar 20) administered via intramuscular injection at Day 1
Cohort 3 (VAX-31): Other prior licensed pneumococcal vaccine or combinationEXPERIMENTALParticipants will receive a single dose of VAX-31 administered via intramuscular injection at Day 1
Cohort 3 (PCV20): Other prior licensed pneumococcal vaccine or combinationACTIVE_COMPARATORParticipants will receive a single dose of PCV20 (Prevnar 20) administered via intramuscular injection at Day 1
VAX-31 + SIVEXPERIMENTALParticipants will receive a single dose of VAX-31 administered as an intramuscular injection at Day 1, concomitantly administered with SIV, followed by placebo at Month 1.
Placebo + SIVEXPERIMENTALParticipants will receive placebo administered via intramuscular injection at Day 1, concomitantly administered with SIV, followed by VAX-31 at Month 1.
Cohort 1 (VAX-31), participant ≥ 50 years of ageEXPERIMENTALParticipants will receive a single dose of VAX-31 administered via intramuscular injection at Day 1
Cohort 1 (PCV21), participant ≥ 50 years of ageACTIVE_COMPARATORParticipants will receive a single dose of PCV21 (Capvaxive) administered via intramuscular injection at Day 1
Cohort 1 (PCV20), participant ≥ 50 years of ageACTIVE_COMPARATORParticipants will receive a single dose of PCV20 (Prevnar 20) administered via intramuscular injection at Day 1
Cohort 2 (VAX-31), participant 18-49 years of ageEXPERIMENTALParticipants will receive a single dose of VAX-31 administered via intramuscular injection at Day 1
Cohort 2 (PCV20), participant 18-49 years of ageACTIVE_COMPARATORParticipants will receive a single dose of PCV20 (Prevnar 20) administered via intramuscular injection at Day 1
VAX-31 LowEXPERIMENTALParticipants will receive 4 doses of VAX-31 administered as an intramuscular injection at 2, 4, 6, and 12-15 months of age at one of four dose levels.
VAX-31 MidEXPERIMENTALParticipants will receive 4 doses of VAX-31 administered as an intramuscular injection at 2, 4, 6, and 12-15 months of age at one of four dose levels.
VAX-31 HighEXPERIMENTALParticipants will receive 4 doses of VAX-31 administered as an intramuscular injection at 2, 4, 6, and 12-15 months of age at one of four dose levels.
PCV20ACTIVE_COMPARATORParticipants 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.
VAX-31 High-PFSEXPERIMENTALParticipants will receive 4 doses of VAX-31 administered as an intramuscular injection at 2, 4, 6, and 12-15 months of age at one of four dose levels.
Group 1EXPERIMENTALParticipants 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 2EXPERIMENTALParticipants 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 3EXPERIMENTALParticipants 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 4ACTIVE_COMPARATORParticipants received a single intramuscular injection of the standard dose of PCV20 at Day 1.

Interventions

NameTypeDescription
31-valent pneumococcal conjugate vaccineBIOLOGICAL0.5 mL of VAX-31 will be administered into the deltoid muscle
PCV20BIOLOGICAL0.5 mL of the 20-valent pneumococcal conjugate vaccine will be administered into the deltoid muscle
Seasonal Influenza Vaccine (SIV) (Flublok)BIOLOGICAL0.5 mL of SIV into the deltoid muscle
PlaceboBIOLOGICAL0.5mL of placebo (normal saline) into the deltoid muscle
31 valent pneumococcal conjugate vaccineBIOLOGICAL0.5 mL of VAX-31 will be administered into the deltoid muscle
PCV21BIOLOGICAL0.5 mL of the 21 valent pneumococcal conjugate vaccine will be administered into the deltoid muscle
0.5 mL of the low dose VAX-31BIOLOGICAL31 valent pneumococcal conjugate vaccine
0.5 mL of the mid dose VAX-31BIOLOGICAL31 valent pneumococcal conjugate vaccine
0.5 mL of the high dose VAX-31BIOLOGICAL31 valent pneumococcal conjugate vaccine
0.5 mL dose of PCV20BIOLOGICAL20 valent pneumococcal conjugate vaccine
0.5 mL of the High-PFS dose VAX-31BIOLOGICAL31 valent pneumococcal conjugate vaccine
20 valent pneumococcal conjugate vaccineBIOLOGICAL0.5 ml dose of PCV20 was administered into the deltoid muscle at Day 1
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Eligibility Criteria

Age Range50 Years to N/A
SexALL
Healthy VolunteersYes
Study Sites30

Inclusion Criteria: * Male or female ≥50 years of age (inclusive) at the time of randomization into the study. * Previous receipt of a licensed pneumococcal vaccine or combination of licensed vaccines, with most recent vaccination ≥1 year prior to randomization; the exception is PCV21, which may ha...

Countries:United StatesPuerto Rico
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Recent Changes (Last 90 Days)

LOWJun 30, 2026NCT07365826lastUpdatePostDate: changed
LOWJun 30, 2026NCT07425392lastUpdatePostDate: changed
LOWJun 30, 2026NCT07365826lastUpdatePostDate: changed
LOWJun 30, 2026NCT07425392lastUpdatePostDate: changed
LOWJun 30, 2026NCT07365826lastUpdatePostDate: changed
LOWJun 30, 2026NCT07425392lastUpdatePostDate: changed

Frequently asked questions about VAX-31

What is VAX-31 used for?

VAX-31 is an investigational pneumococcal vaccine being studied for use in healthy infants. It is designed to help prevent pneumococcal disease, which is caused by Streptococcus pneumoniae bacteria. The vaccine is currently in Phase 2 clinical development and has not yet been approved by regulatory authorities.

What does VAX-31 target?

VAX-31 is a pneumococcal vaccine, meaning it targets Streptococcus pneumoniae bacteria. The vaccine is intended to elicit an immune response against pneumococcal strains to prevent infections such as pneumonia, bacteremia, and meningitis. It is being evaluated for its safety, tolerability, and immunogenicity in infants.

Who makes VAX-31?

VAX-31 is being developed by Vaxcyte, Inc., a biopharmaceutical company traded on the stock exchange under the ticker symbol PCVX. The company is conducting clinical trials to evaluate the vaccine's safety and effectiveness in preventing pneumococcal disease.

What phase is VAX-31 in?

VAX-31 is currently in Phase 2 clinical development. It is an investigational drug, meaning it has not been approved by the FDA or other regulatory agencies. The vaccine is being studied in a clinical trial to assess its safety, tolerability, and immunogenicity in healthy infants.

What clinical trials is VAX-31 in?

VAX-31 is being evaluated in a Phase 2 clinical trial with the identifier NCT06720038. This study is assessing the safety, tolerability, and immunogenicity of VAX-31 in healthy infants. The trial is active but not recruiting, with an enrollment of 900 participants across the United States and Puerto Rico.

Is VAX-31 the same as 0.5 mL of the low dose VAX-31?

Yes, VAX-31 is also known as 0.5 mL of the low dose VAX-31. This alternative name refers to a specific formulation or dosage of the vaccine being tested in clinical trials. Both names refer to the same investigational pneumococcal vaccine developed by Vaxcyte, Inc.