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A Study of Group B Streptococcus 6-Valent Polysaccharide Conjugate Vaccine in Healthy Pregnant Women and Their Infants

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This study is looking at Group B streptococcus disease, which is an infection that can affect newborn babies. Group B streptococcus, often called GBS, is a type of bacteria that can be passed from mothers to their babies during pregnancy or birth. The study will use Group B Streptococcus 6-Valent Polysaccharide Conjugate Vaccine (GBS6), which is a vaccine designed to protect against six different types of GBS bacteria. Some pregnant women in this study will receive this vaccine while others will receive placebo. The vaccine is given as a solution for injection into the muscle.

The purpose of this study is to learn about the safety of the GBS vaccine in pregnant women and their babies, and to measure how well the vaccine helps the mother's body create protective substances called antibodies that can be passed to the baby. These antibodies are measured to see if they could protect infants from GBS infections that can occur in the first days after birth, called early-onset disease, or infections that happen later in the first months of life, called late-onset disease. The study will look at whether the vaccine can create enough antibodies against all six types of GBS bacteria included in the vaccine.

During the study, pregnant women between 24 and 36 weeks of pregnancy will receive either the vaccine or placebo. The study will monitor the pregnant women for any reactions at the injection site such as redness, swelling, or pain, as well as general symptoms like fever, nausea, vomiting, diarrhea, headache, tiredness, muscle pain, and joint pain. Blood samples will be taken from mothers and their babies at different times to measure antibody levels. The babies will be followed after birth to check their health and safety, and to measure the antibodies they received from their mothers through the vaccine.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Receiving the vaccine or placebo

    You will receive a single injection during your pregnancy. The injection will be given when you are between 24 weeks and 36 weeks of pregnancy.

    The injection will be administered into a muscle (intramuscular injection).

    You will receive either the Group B Streptococcus 6-Valent Polysaccharide Conjugate Vaccine or a placebo. A placebo is an inactive substance that looks like the vaccine but contains no active ingredients. This is randomly assigned, meaning neither you nor the study staff will choose which one you receive.

  2. Step 2

    Monitoring for immediate reactions after injection

    After receiving the injection, you will be monitored for any immediate reactions at the injection site and throughout your body.

    Specific reactions that will be assessed include redness, swelling, and pain at the injection site.

    Body-wide symptoms that will be monitored include fever, nausea, vomiting, diarrhea, headache, fatigue, muscle pain, and joint pain.

  3. Step 3

    Ongoing safety monitoring during pregnancy

    Throughout the remainder of your pregnancy, any adverse events will be recorded. An adverse event is any unwanted medical occurrence that happens after receiving the injection.

    Any serious adverse events will be closely monitored. These are medical problems that are life-threatening, require hospitalization, or result in significant disability.

    Any medical visits you have for health concerns (medically attended adverse events) will be documented.

  4. Step 4

    Blood sample collection at birth

    When your baby is born, a blood sample will be collected from your infant.

    This blood sample will be tested to measure the levels of specific antibodies against Group B Streptococcus. Antibodies are proteins produced by the immune system that help protect against infections.

    The blood test will measure antibodies against six different types of Group B Streptococcus bacteria (types Ia, Ib, II, III, IV, and V).

  5. Step 5

    Blood sample collection from you at birth

    A blood sample will also be collected from you at the time of your baby's birth.

    This sample will be tested to measure the levels of antibodies against the six types of Group B Streptococcus bacteria in your blood.

  6. Step 6

    Follow-up blood samples from your infant

    Additional blood samples will be collected from your infant at specified times after birth.

    These samples will measure antibody levels against Group B Streptococcus over time to assess how long the protection lasts.

    The samples will also measure antibody activity (OPA antibody titers), which indicates how well the antibodies can fight the bacteria.

    In some infants, blood samples will also be tested for antibodies to diphtheria and to certain types of bacteria covered by pneumococcal conjugate vaccine.

  7. Step 7

    Safety monitoring of your infant

    Your infant's health and safety will be monitored throughout the study period.

    Any adverse events, serious adverse events, or medically attended adverse events in your infant will be recorded.

    This monitoring will continue until the study concludes, which is estimated to be in August 2028.

Who can join the trial?

10 criteria

  • You must be a healthy pregnant woman who is 49 years old or younger
  • You must be between 24 weeks and 36 weeks pregnant on the day of planned vaccination, which means receiving the study vaccine
  • Your pregnancy must be uncomplicated, meaning without serious medical problems or concerns
  • You must be carrying only one baby, not twins or more
  • You must have no known increased risk of pregnancy complications
  • You must have had a fetal anomaly ultrasound, which is a special scan to check the baby's development, performed at 18 weeks of pregnancy or later that showed no significant problems with the baby
  • You must have test results from this pregnancy showing you do not have HIV, which is a virus that affects the immune system
  • You must have test results from this pregnancy showing you do not have syphilis, which is a type of infection
  • You must have test results from this pregnancy showing you do not have hepatitis B, which is a virus that affects the liver
  • These test results must be documented before you are assigned to a group in the study

Who cannot join the trial?

3 criteria

  • The study information provided does not contain specific exclusion criteria, which are reasons why someone cannot participate in this clinical trial
  • Without detailed exclusion criteria listed in the source data, it is not possible to provide the specific conditions or situations that would prevent participation
  • Generally, clinical trials for vaccines given during pregnancy may exclude participants based on certain health conditions, allergies, or other factors, but these specific details are not included in the available information
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Investigated drugs

  • GBS6

    is an investigational vaccine being tested to protect against Group B Streptococcus (GBS) infections. This vaccine is designed to work against six different types of GBS bacteria (serotypes Ia, Ib, II, III, IV, and V). The vaccine is given to pregnant women during pregnancy with the goal of helping their bodies produce antibodies that can be passed to their babies. These antibodies are intended to help protect newborns from serious GBS infections that can occur in the first days and weeks of life. The study is testing whether the vaccine is safe for pregnant women and their babies, and whether it can create enough antibodies to provide protection against these bacterial infections.

  • Placebo

    is an inactive substance that looks like the vaccine but contains no active ingredients. Some participants will receive the placebo instead of the actual vaccine so researchers can compare the results between the two groups and determine if the vaccine is truly effective.

What is already known about the treatment

GBS6 Vaccine – GBS6 is an investigational multivalent vaccine currently being tested in clinical trials for the prevention of Group B streptococcus disease in newborn infants. The vaccine is administered as an injection to healthy pregnant women during pregnancy, with the goal of transferring protective antibodies to their babies before birth. It works by stimulating the mother's immune system to produce specific antibodies (called anti-CPS IgG) against six different types of Group B streptococcus bacteria (serotypes Ia,Ib, II, III, IV, and V), which then pass through the placenta to protect the infant from both early-onset disease (occurring in the first week of life) and late-onset disease (occurring between 7 and 89 days after birth). This vaccine belongs to the pharmacological class of bacterial polysaccharide vaccines and is designed to prevent serious infections that can affect newborns, including bloodstream infections, pneumonia, and meningitis caused by Group B streptococcus.

Investigated diseases

Group B Streptococcus Disease – Group B streptococcus disease is an infection caused by bacteria called Group B Streptococcus, also known as GBS. This bacteria can cause serious infections in newborn babies, appearing either in the first week of life, called early-onset disease, or after the first week up to three months of age, called late-onset disease. Pregnant women can carry GBS bacteria without showing any symptoms, but they can pass it to their babies during childbirth. In newborns, the infection can affect the blood, lungs, brain, and spinal cord. The disease can progress quickly in infants, leading to severe complications affecting multiple body systems. GBS disease remains a significant health concern for newborns worldwide.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2022-503070-36-00Protocol codeC1091009Estimated enrolment12 000 patientsSponsorPfizer Inc.

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