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A Phase 3, Randomized, Double-Blind, Placebo-Controlled Clinical Study to Evaluate the Safety, Tolerability, and Immunogenicity of VAX-31 Concomitantly Administered With Seasonal Influenza Vaccine in Healthy Subjects 50 Years of Age and Older

0 criteria met from your profileSee at a glance how your profile meets each eligibility criteria.
What is being tested

31-valent pneumococcal conjugate vaccine

+ Seasonal Influenza Vaccine (SIV) (Flublok)
+ Placebo
Biological
Who is being recruted

Bacterial Infections and Mycoses
+7

+ Bacterial Infections
+ Infections
Over 50 Years
+26 Eligibility Criteria
See all eligibility criteria
How is the trial designed

Prevention Study

Phase 3
Interventional
Study Start: January 2026
See protocol details

Summary

Principal SponsorVaxcyte, Inc.
Study ContactClinical Development
Last updated: January 27, 2026
Sourced from a government-validated database.Claim as a partner
Study start date: January 12, 2026Actual date on which the first participant was enrolled.

This is a Phase 3, randomized, double-blind study to evaluate the safety and immunogenicity of VAX-31 and seasonal influenza vaccine in pneumococcal-naïve adults ≥ 50 years when the two vaccines are administered at the same visit or separately.

Official TitleA Phase 3, Randomized, Double-Blind, Placebo-Controlled Clinical Study to Evaluate the Safety, Tolerability, and Immunogenicity of VAX-31 Concomitantly Administered With Seasonal Influenza Vaccine in Healthy Subjects 50 Years of Age and Older 
NCT07365826
Principal SponsorVaxcyte, Inc.
Study ContactClinical Development
Last updated: January 27, 2026
Sourced from a government-validated database.Claim as a partner

Protocol

This section provides details of the study plan, including how the study is designed and what the study is measuring.
Design Details
1300 patients to be enrolledTotal number of participants that the clinical trial aims to recruit.
Prevention Study
Prevention studies aim to stop a disease from developing. They often involve people at risk and test things like vaccines, lifestyle changes, or preventive medications.

How participants are assigned to different groups/arms
In this clinical study, participants are placed into groups randomly, like flipping a coin. This ensures that the study is fair and unbiased, making the results more reliable. By assigning participants by chance, researchers can better compare treatments without external influences.

Other Ways to Assign Participants
Non-randomized allocation: Participants are assigned based on specific factors, such as their medical condition or a doctor's decision.
None (Single-arm trial): If the study has only one group, all participants receive the same treatment, and no allocation is needed.

How treatments are given to participants
Participants are divided into different groups, each receiving a specific treatment at the same time. This helps researchers compare how well different treatments work against each other.

Other Ways to Assign Treatments
Single-group assignment: Everyone gets the same treatment.
Cross-over assignment: Participants switch between treatments during the study.
Factorial assignment: Participants receive different combinations of treatments.
Sequential assignment: Participants receive treatments one after another in a specific order, possibly based on individual responses.
Other assignment: Treatment assignment does not follow a standard or predefined design.

How the effectiveness of the treatment is controlled
In a non placebo-controlled study, no participants receive an inert substance (placebo) to compare outcomes. Instead, all participants receive either the experimental treatment or an alternative treatment (often the Standard of Care). This method allows researchers to compare the effects of the experimental treatment with those of a different active intervention, rather than a placebo.

Other Options
Placebo-Controlled: A placebo is used to compare the effects of the experimental treatment with those of an inert substance, isolating the true treatment effect.

How the interventions assigned to participants is kept confidential
Participants, researchers, outcome assessors, and care providers do not know which treatment is being given. This is the most complete way to prevent bias and keep the study as neutral as possible.

Other Ways to Mask Information
Open-label: Everyone knows which treatment is being given.
Single-blind: Participants do not know which treatment they are receiving, but researchers do.
Double-blind: Neither participants nor researchers know which treatment is given.
Triple-blind: Participants, researchers, and outcome assessors do not know which treatment is given.

Eligibility

Researchers look for people who fit a certain description, called eligibility criteria: person's general health condition or prior treatments.
Conditions
Criteria
Any sexBiological sex of participants that are eligible to enroll.
Over 50 YearsRange of ages for which participants are eligible to join.
Healthy volunteers allowedIf individuals who are healthy and do not have the condition being studied can participate.
Conditions
Pathology
Bacterial Infections and Mycoses
Bacterial Infections
Infections
Lung Diseases
Pneumococcal Infections
Pneumonia
Respiratory Tract Diseases
Respiratory Tract Infections
Streptococcal Infections
Gram-Positive Bacterial Infections
Criteria
8 inclusion criteria required to participate
Male or female ≥50 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 at 7 months after the first study vaccination.
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.

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18 exclusion criteria prevent from participating
History of IPD or pneumococcal pneumonia (either confirmed or self-reported) at any age.
Previous receipt of a licensed or investigational pneumococcal vaccine at any age.
Previous receipt of an influenza vaccine from the current season; receipt of any influenza vaccine (licensed or investigational) within 6 months prior to Day 1; or receipt/planned receipt of any licensed or investigational non-study influenza vaccine during study participation.
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.

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Study Plan

Find out more about all the medication administered in this study, their detailed description and what they involve.
Treatment Groups
Study Objectives
2 intervention groups 

are designated in this study

This study does not include a placebo group 

Treatment Groups
Group I
Experimental
Participants will receive placebo administered via intramuscular injection at Day 1, concomitantly administered with SIV, followed by VAX-31 at Month 1.

0.5 mL of VAX-31 will be administered into the deltoid muscle

0.5 mL of SIV into the deltoid muscle

0.5mL of placebo (normal saline) into the deltoid muscle
Group II
Experimental
Participants 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.

0.5 mL of VAX-31 will be administered into the deltoid muscle

0.5 mL of SIV into the deltoid muscle

0.5mL of placebo (normal saline) into the deltoid muscle
Study Objectives
Primary Objectives

Study Centers

These are the hospitals, clinics, or research facilities where the trial is being conducted. You can find the location closest to you and its status.
This study has 25 locations
Recruiting
Hope Research InstitutePhoenix, United StatesSee the location
Recruiting
Tekton Research at Fort CollinsFort Collins, United States
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University Clinical Research - DelandDeLand, United States
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CenExel Research Centers of AmericaHollywood, United States
Recruiting
25 Study Centers
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