Group B Streptococcal InfectionsPhase 2NCT04258995

A TRIAL TO EVALUATE THE SAFETY, TOLERABILITY, AND IMMUNOGENICITY OF A BOOSTER DOSE OF A GROUP B STREPTOCOCCUS 6 VALENT POLYSACCHARIDE CONJUGATE VACCINE (GBS6) IN HEALTHY ADULTS

A Phase 2 study testing Group B streptoccous 6-valent polysaccharide conjugate vaccine (GBS6) in people with Group B Streptococcal Infections, run by Pfizer at 4 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

This study is an extension to the completed first-in-human C1091001 study (NCT03170609) and is to evaluate the safety and immunogenicity of a single booster vaccine dose of GBS6, administered approximately 2 years or more after a primary GBS6 dose, to healthy adult males and nonpregnant women. Read more about this study

Who is it for?: Ages 20 to 51 yearsHealthy volunteers can take part
Conditions the study is for: Group B Streptococcal Infections
What is being tested?: Group B streptoccous 6-valent polysaccharide conjugate vaccine (GBS6)
Type of treatment: Vaccines
Could I receive a placebo?: No, everyone receives an active treatment
How many people: 151 participants
Where: 4 sitesUnited States
Study dates: 11 Feb 2020to 15 Sep 2020
Phase: Phase 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 20 to 51 years
All sexes
Healthy volunteers accepted
Adult

Who may be able to join

Healthy adults (male and female) at enrollment who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study.
Participants who were enrolled in the C1091001 study, received GBS6, and completed the 1-month blood draw.

Who cannot join

Pregnant female participants; breastfeeding female participants; positive urine pregnancy test for women of childbearing potential (WOCBP) at Visit 1 (prior to vaccination); and WOCBP who are, in the opinion of the investigator, sexually active and at risk for pregnancy and fertile men and WOCBP who are unwilling or unable to use effective methods of contraception as outlined in this protocol from the signing of the informed consent until at least 3 months after the last dose of investigational product.
Acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the participant inappropriate for entry into this study. Chronic medical conditions include human immunodeficiency virus, chronic hepatitis B virus (HBV) infection (HBV surface antigen positive), and/or hepatitis C virus infection.
History of severe adverse reaction and/or severe allergic reaction (eg, anaphylaxis) to any vaccine.
History of microbiologically proven invasive disease caused by group B streptococcus (Streptococcus agalactiae).
Previous vaccination with any licensed or investigational group B streptococcus vaccine (other than GBS6), or planned receipt during the participant's participation in the study (through 6-month telephone call).

Trial locations and contacts

4 sites in 1 country.

United States4 sites

Kentucky Pediatric & Adult Research Inc.
Bardstown, Kentucky, 40004
J. Lewis Research, Inc./ Foothill Family Clinic South
Salt Lake City, Utah, 84109
J. Lewis Research, Inc. / Foothill Family Clinic South
Salt Lake City, Utah, 84121
Clinical Research Atlanta
Stockbridge, Georgia, 30281

Other trials in United States

About this study

Official title: A PHASE 2, OPEN-LABEL TRIAL TO EVALUATE THE SAFETY, TOLERABILITY, AND IMMUNOGENICITY OF A BOOSTER DOSE OF A GROUP B STREPTOCOCCUS 6 VALENT POLYSACCHARIDE CONJUGATE VACCINE (GBS6) IN HEALTHY ADULTS

Conditions: Group B Streptococcal Infections
Being tested: Group B streptoccous 6-valent polysaccharide conjugate vaccine (GBS6)
Medical subject headings: Streptococcal Infections

What participants receive

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

Group B streptoccous 6-valent polysaccharide conjugate vaccine (GBS6)Biological
Also called GBS6
2 formulations at 1 dose level

Study groups in NCT04258995
Study group	Role	What they receive
GBS6 no aluminum phosphate (GBS6 no AlPO4)	Experimental	Not described Receives: Biological: Group B streptoccous 6-valent polysaccharide conjugate vaccine (GBS6)
GBS6 with aluminum phosphate (GBS6 with AlPO4)	Experimental	Not described Receives: Biological: Group B streptoccous 6-valent polysaccharide conjugate vaccine (GBS6)

What is being measured

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

Percentage of Participants Reporting Prompted Local Reactions Within 14 Days Following Booster Dose (Redness, Swelling, and Pain at the Injection Site)
Local reactions were collected by using an e-diary and included pain at injection site, redness, and swelling graded below: pain at injection site: mild (did not interfere with activity), moderate (repeated use of nonnarcotic pain reliever >24 hours or interfered with activity), severe (any use of narcotic pain reliever or prevented daily activity), grade 4 (emergency room visit or hospitalization). Redness and swelling were graded as: mild (2.0-5.0 centimeter [cm]), moderate (greater than [>] 5.0-10.0 cm),severe (>10.0 cm), grade 4 for redness (necrosis or exfoliative dermatitis) and grade 4 for swelling (necrosis).Maximum severity (highest grading) of each location reaction within 14 days of vaccination was derived.
Measured: Within 14 days after booster dose
Percentage of Participants Reporting Prompted Systemic Events Within 14 Days Following Booster Dose (Fever, Nausea/Vomiting, Diarrhea, Headache, Fatigue, Muscle Pain, and Joint Pain)
Nausea/Vomiting:Mild:No interference with activity or 1-2 times in 24 hours;Moderate:Some interference with activity or>2 times in 24 hours;Severe:Prevented daily activity, required IV hydration.Diarrhea:Mild:2-3 loose stools in 24 hours;Moderate: 4-5 loose stools in 24 hours;Severe:>=6 loose stools in 24 hours.Headache:Mild:No interference with activity;Moderate:Repeated use of nonnarcotic pain reliever >24 hours or some interference with activity;Severe:Significant; any use of narcotic pain reliever or prevents daily activity.Fatigue:Mild:No interference with activity;Moderate: Some interference with activity;Severe: Significant; prevented daily activity.Muscle pain:Mild: No interference with activity;Moderate:Some interference with activity;Severe:Significant;prevented daily activity.Muscle/joint pain:Mild: No interference with activity;Moderate:Some interference with activity;Severe:Significant; prevented daily activity.Grade 4 for all AEs:Emergency visit or hospitalization.
Measured: Within 14 days after booster dose
Percentage of Participants Reporting Adverse Events (AEs) Within 1 Month Following Booster Dose
An AE was any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. Serious adverse event (SAE) was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly or that was considered to be an important medical event. AEs included both non-serious AEs and SAEs.
Measured: Within 1 month after booster dose
Percentage of Participants Reporting Medically Attended Adverse Events (MAEs) Within 6 Months Following Booster Dose
An AE was any untoward medical occurrence in a participant in a participant who received investigational product without regard to possibility of causal relationship. SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly or that was considered to be an important medical event. An MAE was defined as a non serious AE (AE other than SAE) that resulted in an evaluation at a medical facility.
Measured: Within 6 months after booster dose
Percentage of Participants With Serious Adverse Events (SAEs) Within 6 Months After Booster Dose
An AE was any untoward medical occurrence in a participant in a participant who received investigational product without regard to possibility of causal relationship. SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly or that was considered to be an important medical event.
Measured: Within 6 months after booster dose

Secondary outcomes (5)

GBS Serotype-Specific IgG Geometric Mean Concentrations (GMC) Measured Before and 1 Month After Booster Dose
Serotypes used for evaluation were: Ia, Ib, II, III, IV, and V.
Measured: Before and 1 month after booster dose
GBS Serotype-Specific Opsonophagocytic Activity (OPA) Geometric Mean Titers Measured Before to 1 Month After Booster Dose
OPA for the 6 serotypes (Ia, Ib, II, III, IV, V) were determined in all participants for each blood sample at Day 1 and at 1 month after booster dose.
Measured: Within 6 months after primary dose and within 1 month after booster dose
GBS Serotype-Specific IgG Geometric Mean Fold Rise (GMFR) From Before To 1 Month After Booster Dose
IgG for the 6 serotypes (Ia, Ib, II, III, IV, V) were determined in all participants for each blood sample at Day 1 and at 1 month after booster dose.
Measured: 1 month after booster dose
GBS Serotype-Specific OPA GMFR Measured Before and 1 Month After Booster Dose
OPA for the 6 serotypes (Ia, Ib, II, III, IV, V) were determined in all participants for each blood sample at Day 1 and at 1 month after booster dose.
Measured: 1 month after booster dose
GBS Serotype-Specific IgG GMC Measured 1 Month After Booster Dose Stratified by Baseline Pre-vaccination Status (Before the Primary Dose)
Serotypes used for evaluation were: Ia, Ib, II, III, IV, and V. The pre-vaccination immunogenicity blood draw and booster vaccination were both performed on Day 1.
Measured: 1 month after booster dose

Timeline

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

11 Feb 202015 Sep 2020

First posted6 Feb 2020
Study start11 Feb 2020
Primary completion15 Sep 2020
Study completion15 Sep 2020

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 Group B Streptococcal InfectionsStudies of the same condition, open and under way.
More trials run by PfizerThe sponsor's other registered studies.
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 2
Primary purpose: Prevention
Allocation: Non-randomised
Intervention model: Parallel groups
Model description: There are two arms in the study however based on the prior formulation received participants can only be enrolled into one predetermined arm in the study. Participants are assigned by an interactive response technology (IRT) based on prior formulation received.
Masking: None (open label)
Enrolment: 151 participants (actual)

IDs, dates and publications

ClinicalTrials.gov ID: NCT04258995
Sponsor's protocol ID: C1091007
Status last verified: Oct 2021
First submitted: 4 Feb 2020
Last updated: 13 Oct 2021
Results posted: Yes, on ClinicalTrials.gov
Data monitoring committee: Yes
FDA-regulated drug: Yes
FDA-regulated device: No
Individual data sharing: Yes: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical\_trials/trial\_data\_and\_results/data\_requests.

Publications

Jongihlati B, Segall N, Block SL, Absalon J, Perez J, Munson S, Sanchez-Pearson Y, Simon R, Silmon de Monerri NC, Radley D, McLaughlin LC, Gaylord M, Gruber WC, Jansen KU, Scott DA, Anderson AS. Safety and immunogenicity of a booster dose of a novel hexavalent group B streptococcus conjugate vaccine in healthy, non-pregnant adults: a phase 2, open-label extension of a phase 1/2 randomised controlled trial. Lancet Infect Dis. 2025 Oct;25(10):1138-1148. doi: 10.1016/S1473-3099(25)00216-6. Epub 2025 Jun 13.
PubMed 40523378

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?

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All Group B Streptococcal Infections trials

Study at a glance

From the registry record, last updated by the sponsor on 13 Oct 2021. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: A PHASE 2, OPEN-LABEL TRIAL TO EVALUATE THE SAFETY, TOLERABILITY, AND IMMUNOGENICITY OF A BOOSTER DOSE OF A GROUP B STREPTOCOCCUS 6 VALENT POLYSACCHARIDE CONJUGATE VACCINE (GBS6) IN HEALTHY ADULTS
ClinicalTrials.gov ID: NCT04258995
Acronym / sponsor ID: C1091007
Conditions: Group B Streptococcal Infections
Phase: Phase 2
Study type: Interventional
Recruitment status: Completed
Enrolment: 151 participants (actual)
Lead sponsor: PfizerIndustry (pharma, biotech, devices)
Study start: 11 Feb 2020 (actual)
Primary completion: 15 Sep 2020 (actual)
Study completion: 15 Sep 2020 (actual)
First posted: 6 Feb 2020 (actual)
Results: Posted 13 Oct 2021

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: Non-randomised
Intervention model: Parallel groups
Masking: None (open label)
Number of arms: 2
Model description: There are two arms in the study however based on the prior formulation received participants can only be enrolled into one predetermined arm in the study. Participants are assigned by an interactive response technology (IRT) based on prior formulation received.

Arm	Type	Receives
GBS6 no aluminum phosphate (GBS6 no AlPO4)	Experimental	Biological: Group B streptoccous 6-valent polysaccharide conjugate vaccine (GBS6)
GBS6 with aluminum phosphate (GBS6 with AlPO4)	Experimental	Biological: Group B streptoccous 6-valent polysaccharide conjugate vaccine (GBS6)

Who may qualify

Ages: 20 to 51 years
Sex: All
Healthy volunteers: Accepted
Age groups: Adult

Key inclusion criteria (2 listed)

Healthy adults (male and female) at enrollment who are determined by medical history, physical examination, and clinical judgment of the investigator to be eligible for inclusion in the study.
Participants who were enrolled in the C1091001 study, received GBS6, and completed the 1-month blood draw.

Key exclusion criteria (5 listed)

Pregnant female participants; breastfeeding female participants; positive urine pregnancy test for women of childbearing potential (WOCBP) at Visit 1 (prior to vaccination); and WOCBP who are, in the opinion of the investigator, sexually active and at risk for pregnancy and fertile men and WOCBP who are unwilling or unable to use effective methods of contraception as outlined in this protocol from the signing of the informed consent until at least 3 months after the last dose of investigational product.
Acute or chronic medical or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation or investigational product administration or may interfere with the interpretation of study results and, in the judgment of the investigator, would make the participant inappropriate for entry into this study. Chronic medical conditions include human immunodeficiency virus, chronic hepatitis B virus (HBV) infection (HBV surface antigen positive), and/or hepatitis C virus infection.
History of severe adverse reaction and/or severe allergic reaction (eg, anaphylaxis) to any vaccine.
History of microbiologically proven invasive disease caused by group B streptococcus (Streptococcus agalactiae).
Previous vaccination with any licensed or investigational group B streptococcus vaccine (other than GBS6), or planned receipt during the participant's participation in the study (through 6-month telephone call).

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
Group B streptoccous 6-valent polysaccharide conjugate vaccine (GBS6)Also: GBS62 formulations at 1 dose level	Biological	GBS6 no aluminum phosphate (GBS6 no AlPO4), GBS6 with aluminum phosphate (GBS6 with AlPO4)

Primary outcome

Percentage of Participants Reporting Prompted Local Reactions Within 14 Days Following Booster Dose (Redness, Swelling, and Pain at the Injection Site)
Time frame: Within 14 days after booster dose
Local reactions were collected by using an e-diary and included pain at injection site, redness, and swelling graded below: pain at injection site: mild (did not interfere with activity), moderate (repeated use of nonnarcotic pain reliever >24 hours or interfered with activity), severe (any use of narcotic pain reliever or prevented daily activity), grade 4 (emergency room visit or hospitalization). Redness and swelling were graded as: mild (2.0-5.0 centimeter [cm]), moderate (greater than [>] 5.0-10.0 cm),severe (>10.0 cm), grade 4 for redness (necrosis or exfoliative dermatitis) and grade 4 for swelling (necrosis).Maximum severity (highest grading) of each location reaction within 14 days of vaccination was derived.
Percentage of Participants Reporting Prompted Systemic Events Within 14 Days Following Booster Dose (Fever, Nausea/Vomiting, Diarrhea, Headache, Fatigue, Muscle Pain, and Joint Pain)
Time frame: Within 14 days after booster dose
Nausea/Vomiting:Mild:No interference with activity or 1-2 times in 24 hours;Moderate:Some interference with activity or>2 times in 24 hours;Severe:Prevented daily activity, required IV hydration.Diarrhea:Mild:2-3 loose stools in 24 hours;Moderate: 4-5 loose stools in 24 hours;Severe:>=6 loose stools in 24 hours.Headache:Mild:No interference with activity;Moderate:Repeated use of nonnarcotic pain reliever >24 hours or some interference with activity;Severe:Significant; any use of narcotic pain reliever or prevents daily activity.Fatigue:Mild:No interference with activity;Moderate: Some interference with activity;Severe: Significant; prevented daily activity.Muscle pain:Mild: No interference with activity;Moderate:Some interference with activity;Severe:Significant;prevented daily activity.Muscle/joint pain:Mild: No interference with activity;Moderate:Some interference with activity;Severe:Significant; prevented daily activity.Grade 4 for all AEs:Emergency visit or hospitalization.
Percentage of Participants Reporting Adverse Events (AEs) Within 1 Month Following Booster Dose
Time frame: Within 1 month after booster dose
An AE was any untoward medical occurrence in a participant who received investigational product without regard to possibility of causal relationship. Serious adverse event (SAE) was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly or that was considered to be an important medical event. AEs included both non-serious AEs and SAEs.
Percentage of Participants Reporting Medically Attended Adverse Events (MAEs) Within 6 Months Following Booster Dose
Time frame: Within 6 months after booster dose
An AE was any untoward medical occurrence in a participant in a participant who received investigational product without regard to possibility of causal relationship. SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly or that was considered to be an important medical event. An MAE was defined as a non serious AE (AE other than SAE) that resulted in an evaluation at a medical facility.
Percentage of Participants With Serious Adverse Events (SAEs) Within 6 Months After Booster Dose
Time frame: Within 6 months after booster dose
An AE was any untoward medical occurrence in a participant in a participant who received investigational product without regard to possibility of causal relationship. SAE was an AE resulting in any of the following outcomes or deemed significant for any other reason: death; initial or prolonged inpatient hospitalization; life-threatening experience (immediate risk of dying); persistent or significant disability/incapacity; congenital anomaly or that was considered to be an important medical event.

5 secondary outcomes

GBS Serotype-Specific IgG Geometric Mean Concentrations (GMC) Measured Before and 1 Month After Booster Dose
Time frame: Before and 1 month after booster dose
GBS Serotype-Specific Opsonophagocytic Activity (OPA) Geometric Mean Titers Measured Before to 1 Month After Booster Dose
Time frame: Within 6 months after primary dose and within 1 month after booster dose
GBS Serotype-Specific IgG Geometric Mean Fold Rise (GMFR) From Before To 1 Month After Booster Dose
Time frame: 1 month after booster dose
GBS Serotype-Specific OPA GMFR Measured Before and 1 Month After Booster Dose
Time frame: 1 month after booster dose
GBS Serotype-Specific IgG GMC Measured 1 Month After Booster Dose Stratified by Baseline Pre-vaccination Status (Before the Primary Dose)
Time frame: 1 month after booster dose

Results and safety

Results posted to the registry on 13 Oct 2021, as reported by the sponsor. Figures are copied from the record, not re-analysed. Full results on ClinicalTrials.gov.

Participant flow

Group	Started	Completed
GBS6 20 μg With AlPO4	76	75
GBS6 20 μg Without AlPO4	75	74

Primary outcome: Percentage of Participants Reporting Prompted Local Reactions Within 14 Days Following Booster Dose (Redness, Swelling, and Pain at the Injection Site)

Time frame: Within 14 days after booster dose. Number (95% Confidence Interval). Unit: Percentage of participants

Measure	GBS6 20 μg With AlPO4 n = 76	GBS6 20 μg Without AlPO4 n = 75
Pain at injection site: Any	68.4 (56.7 to 78.6)	42.7 (31.3 to 54.6)
Pain at injection site: Mild	53.9 (42.1 to 65.5)	38.7 (27.6 to 50.6)
Pain at injection site: Moderate	11.8 (5.6 to 21.3)	4.0 (0.8 to 11.2)
Pain at injection site: Severe	2.6 (0.3 to 9.2)	0 (0.0 to 4.8)
Pain at injection site: Grade 4	0 (0.0 to 4.7)	0 (0.0 to 4.8)
Redness: Any	3.9 (0.8 to 11.1)	2.7 (0.3 to 9.3)
Redness: Mild	3.9 (0.8 to 11.1)	2.7 (0.3 to 9.3)
Redness: Moderate	0 (0.0 to 4.7)	0 (0.0 to 4.8)

Population analysed: All the participants reporting "yes" or "no" for at least 1 day were included in the analysis.

Primary outcome: Percentage of Participants Reporting Prompted Systemic Events Within 14 Days Following Booster Dose (Fever, Nausea/Vomiting, Diarrhea, Headache, Fatigue, Muscle Pain, and Joint Pain)

Time frame: Within 14 days after booster dose. Number (95% Confidence Interval). Unit: percentage of participants

Measure	GBS6 20 μg With AlPO4 n = 76	GBS6 20 μg Without AlPO4 n = 75
Fever:>=38.0 degree C	3.9 (0.8 to 11.1)	1.3 (0.0 to 7.2)
Fever: 38.0°C to 38.4°C	1.3 (0.0 to 7.1)	0 (0.0 to 4.8)
Fever: >38.4°C to 38.9°C	2.6 (0.3 to 9.2)	1.3 (0.0 to 7.2)
Fever: >38.9°C to 40.0°C	0 (0.0 to 4.7)	0 (0.0 to 4.8)
Fever: >40.0°C	0 (0.0 to 4.7)	0 (0.0 to 4.8)
Nausea/vomiting: Any	7.9 (3.0 to 16.4)	10.7 (4.7 to 19.9)
Nausea/vomiting: Mild	6.6 (2.2 to 14.7)	5.3 (1.5 to 13.1)
Nausea/vomiting: Moderate	1.3 (0.0 to 7.1)	5.3 (1.5 to 13.1)

Population analysed: All the participants reporting "yes" or "no" for at least 1 day were included in the analysis.

Primary outcome: Percentage of Participants Reporting Adverse Events (AEs) Within 1 Month Following Booster Dose

Time frame: Within 1 month after booster dose. Number (95% Confidence Interval). Unit: percentage of participants

Measure	GBS6 20 μg With AlPO4 n = 76	GBS6 20 μg Without AlPO4 n = 75
Value	6.6 (2.2 to 14.7)	12.0 (5.6 to 21.6)

Population analysed: Safety population included all participants who received 1 booster dose and had at least 1 safety assessment after receiving the booster dose.

Primary outcome: Percentage of Participants Reporting Medically Attended Adverse Events (MAEs) Within 6 Months Following Booster Dose

Time frame: Within 6 months after booster dose. Number (95% Confidence Interval). Unit: percentage of participants

Measure	GBS6 20 μg With AlPO4 n = 76	GBS6 20 μg Without AlPO4 n = 75
Value	11.8 (5.6 to 21.3)	9.3 (3.8 to 18.3)

Population analysed: Safety population included all participants who received 1 booster dose and had at least 1 safety assessment after receiving the booster dose.

5 secondary outcomes are reported in the full results.

Adverse events

Time frame: The time period for actively eliciting and collecting AEs and SAEs for each participant began from the time the participant provided informed consent, through and including Visit 2 (1 month after booster dose) for AEs and through and including Visit 3 for MAEs and SAEs (6 months after booster dose).. Other adverse events reported at 5% frequency or more

Group	Serious adverse events	Other adverse events	Deaths
GBS6 20 μg With AlPO4	1 of 76 (1.3%)	59 of 76 (77.6%)	0 of 76
GBS6 20 μg Without AlPO4	0 of 75 (0%)	54 of 75 (72%)	0 of 75

Loading the posted results from ClinicalTrials.gov…

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 13 Oct 2021.
Posted resultsParticipant flow, baseline, all outcome measures and adverse events.
Derived from this study: PubMed 40523378Jongihlati B, Segall N, Block SL, Absalon J, Perez J, Munson S, Sanchez-Pearson Y, Simon R, Silmon de Monerri NC, Radley D, McLaughlin LC, Gaylord M, Gruber WC, Jansen KU, Scott DA, Anderson AS. Safety and immunogenicity of a booster dose of a novel hexavalent group B streptococcus conjugate vaccine in healthy, non-pregnant adults: a phase 2, open-label extension of a phase 1/2 randomised controlled trial. Lancet Infect Dis. 2025 Oct;25(10):1138-1148. doi: 10.1016/S1473-3099(25)00216-6. Epub 2025 Jun 13.
To obtain contact information for a study center near you, click here.Link provided by the sponsor.
Individual participant dataSharing planned: Yes. Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.

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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.

Pfizer CT.gov Call Center study director

Pfizer

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

Questions about this trial

What is this clinical trial studying?

A Phase 2 study testing Group B streptoccous 6-valent polysaccharide conjugate vaccine (GBS6) in people with Group B Streptococcal Infections, run by Pfizer at 4 sites in United States.

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 2 inclusion and 5 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 13 Oct 2021. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 4 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 phase mean?

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 13 Oct 2021). 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 Participants Reporting Prompted Local Reactions Within 14 Days Following Booster Dose (Redness, Swelling, and Pain at the Injection Site) (time frame: Within 14 days after booster dose). The study lists 5 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 NCT04258995, 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 13 Oct 2021.