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Safety and Immune Response of GBS‑NN/NN2 Vaccine in Pregnant Women and Their Infants to Prevent Group B Streptococcus Infection

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What is this study about?

The trial looks at preventing infection caused by Group B streptococcus infection, which can affect newborns if a mother carries the bacteria. The vaccine being tested, GBS‑NN/NN2, is given as a small injection into the muscle (intramuscular) during pregnancy, while some participants receive a saline solution called placebo instead of the vaccine.

The main purpose is to determine whether the vaccine can safely create protective immune responses in both the mother and the baby, measured by the level of protective antibodies at birth.

Pregnant volunteers receive one dose of the assigned injection in the later part of pregnancy, after which they and their infants are followed with routine check‑ups after delivery. A small blood sample is taken from the baby at birth to assess immunity, and any health problems or serious side effects are recorded during the short follow‑up period.

1 randomisation and assignment

after joining the study you will be randomly placed into one of two groups. one group receives the investigational vaccine GBS‑NN/NN2, the other group receives a placebo consisting of 0.9% sodium chloride, an inactive saline solution.

2 administration of the injection

you will receive a single intramuscular injection. the vaccine dose is 50 µg (micrograms) of the GBS‑NN/NN2 suspension. the placebo injection contains the same volume of saline but no active substance.

the injection is given into a muscle, usually in the upper arm, by a trained health professional.

3 immediate safety observation

after the injection you will be observed for a short period (typically 30 minutes) so that any immediate reactions can be recognised and treated promptly.

4 routine follow‑up visits during pregnancy

you will attend scheduled visits with the study team while you remain pregnant. at each visit you will be asked about any new symptoms, discomfort, or other health changes that might be related to the injection.

the purpose of these visits is to monitor for adverse events (any unwanted medical occurrences) and to ensure your safety and the safety of your baby.

5 birth and infant blood sample

when your baby is born a small blood sample will be taken from the infant. this sample is used to measure functional antibody titres, which indicate how well the infant’s immune system may be protected against group B streptococcus.

the measurement is performed at birth to assess the immune response generated by the maternal vaccination.

6 post‑delivery safety monitoring

after delivery you and your infant will continue to be monitored for a period defined by the study protocol. you will be asked to report any health problems, and the infant will be checked for signs of infection or other concerns.

the study team will record any serious adverse events (SAEs) or events of special interest (AESIs) that occur in either you or the baby.

7 final study assessment

at the end of the study period a final visit will be scheduled. during this visit the study team will review all collected information, confirm the safety outcomes, and complete any remaining laboratory analyses.

Who Can Join the Study?

  • Be pregnant with a single baby (not twins) and be about 24 weeks pregnant (give or take a few days) when the first vaccine dose is planned. Pregnancy dating should be based on the first day of your last menstrual period confirmed by an early ultrasound, or on an early ultrasound if the last period date is unknown.
  • Be between 18 and 49 years old and have a body mass index (BMI) greater than 17.5 but less than 40 kg/m². BMI is a simple calculation that compares your weight to your height.
  • Have had an ultrasound exam of the baby at 18 weeks of pregnancy or later that showed no major abnormalities.
  • Be willing to give written permission (parental consent) to take part in the study, following the International Council for Harmonisation (ICH) guidelines on Good Clinical Practice (GCP) and local laws.
  • Be able to attend all scheduled study visits, follow the study procedures, and plan to deliver the baby at a hospital or birthing facility where the study can be carried out.

Who Cannot Join the Study?

  • You have ever had a severe allergic reaction called anaphylaxis after receiving any vaccine.
  • You have had an allergic reaction (such as a rash or anaphylaxis) to any ingredient of the GBS‑NN/NN2 Vaccine.
  • Blood tests during this pregnancy show you have syphilis, human immunodeficiency virus (HIV), or an active hepatitis B infection.
  • You are known or suspected to have an infection during pregnancy with any of the following: toxoplasma, parvovirus B19, malaria, Zika, rubella, varicella (chickenpox), cytomegalovirus, or genital herpes simplex.
  • You have a confirmed invasive disease caused by Group B streptococcus (GBS) in this pregnancy, meaning the bacteria were found in a sterile site such as blood, spinal fluid, or joint fluid.
  • You have a bleeding disorder or a condition that makes you bleed for a long time, which would make an intramuscular injection unsafe.
  • You have any psychiatric condition, including recent thoughts of suicide or self‑harm, that could increase the risk of taking part in the study.
  • You have taken part in another clinical trial using an experimental drug or device within the past 28 days, or you are planning to be in another such trial while this one is ongoing.
  • You have any skin lesion or tattoo on the arms where the injection would be given that would prevent proper evaluation of the injection site.
  • At the screening visit you know you are carrying a fetus that is malformed or has a genetic abnormality.
  • You have current pregnancy complications or abnormalities that, in the investigator’s opinion, raise the risk of participating in the trial.
  • You have had previous pregnancy complications or abnormalities that the investigator believes increase the risk of taking part in the study.
  • You have a known or suspected weakened immune system (immunodeficiency) or cancer, or a family history of a congenital (present at birth) or hereditary (inherited) immunodeficiency.
  • You have taken immune‑suppressing or immune‑modifying medicines continuously for more than 14 days within the 6 months before the first dose.
  • You have a serious acute or chronic health problem that is not well controlled.
  • You have received blood, blood products, plasma derivatives, or any immunoglobulin (antibody) preparations in the 12 weeks before the first dose, or you plan to receive any of these during the trial.
  • You have a clinically important level of anemia (low red blood cell count) as judged by the study staff.
  • You have previously been vaccinated with any approved or experimental GBS vaccine, or you plan to receive such a vaccine during the study period.

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name City Country Status
Université Libre de Bruxelles – Hôpital Erasme Brussels Belgium

Other Sites

Site Name City Country Status
Fakultni Nemocnice Hradec Kralove Novy Hradec Kralove Czechia
Ugtihexbbh Od Aossjue Edegem Belgium
Urakjwkrpoks Zewhihbikz Gkmu Gent Belgium
Ohazen Uhidqvorwd Hijjrkts Odense Denmark
Rdtsqg Mmuurvbgtyu Aarhus Denmark
Hrekjszz Hkcxnuht Hvidovre Denmark

Want to learn more about this study or check if you can participate? Contact us.

Trial status

Country Status Recruitment Start
Belgium Belgium
Not yet recruiting
02.10.2026
Czechia Czechia
Not yet recruiting
02.10.2026
Denmark Denmark
Not yet recruiting
02.10.2026

Trial locations

GBS-NN/NN2 is an experimental vaccine being studied to protect newborn babies from infections caused by Group B Streptococcus. The vaccine is given as an injection into the muscle of pregnant women. It contains two parts, called GBS‑NN and GBS‑NN2, which work together to stimulate the mother’s immune system. This helps the mother produce antibodies that can cross the placenta and give the baby protection right after birth. In the trial, researchers will watch for any serious side effects and will measure how well the vaccine creates antibodies that can keep infants safe from this infection.

Group B streptococcal infection – Group B streptococcal infection is caused by the bacterium Streptococcus agalactiae, which commonly lives in the lower intestine and vagina of healthy adults. During childbirth the bacteria can be passed from a colonized mother to her baby. In newborns the infection can appear within the first week (early‑onset) or later in the first three months (late‑onset). The bacteria can spread through the bloodstream and affect the lungs, brain, or other organs, leading to symptoms such as fever, breathing trouble, or irritability. Without treatment the infection can progress from localized to widespread involvement of multiple organ systems.

Trial ID:
2026-525385-21-00
Protocol code:
MVX010
Trial Phase:
Therapeutic use (Phase IV)

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