Study of RSV vaccine and nirsevimab combination to prevent RSV infection in infants up to 12 months of age

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What is this study about?

This study is looking at ways to protect infants from Respiratory Syncytial Virus, which is a common virus that can cause breathing problems in babies. The study will use three different products: Beyfortus 50 mg and 100 mg, which are solutions given as injections into the muscle that contain nirsevimab, and Abrysvo, which is a vaccine also given as an injection into the muscle. Nirsevimab is a type of medicine that helps the body fight off the virus, while Abrysvo is a vaccine that helps the body build protection against the virus. The purpose of this study is to find out if giving pregnant women the vaccine along with giving their babies the nirsevimab injection at 4 months of age provides better protection against breathing infections caused by this virus compared to giving babies only the nirsevimab injection during their first season when the virus is common, or compared to giving pregnant women only the vaccine.

In this study, pregnant women between 24 and 36 weeks of pregnancy may receive the vaccine during pregnancy, and their babies may receive the nirsevimab injection after birth, depending on which group they are assigned to. The study will follow the babies until they are 12 months old to see if they develop breathing infections caused by the virus. The main thing the researchers will look at is whether babies develop breathing infection symptoms along with a positive test for the virus by the time they reach 12 months of age.

Women who take part will need to be willing to follow all study requirements and complete surveys throughout the study period. The study is expected to start enrolling participants in 2025 and continue until 2029. Both mothers and their babies will be monitored during this time to collect information about any infections and the safety of the treatments used.

1 Enrollment during pregnancy

Your participation begins when you are pregnant, between 24 weeks and 36 weeks plus 6 days of pregnancy. The exact starting week may vary based on national guidance in your country.

At this stage, informed consent will be provided. You will need to confirm that you are willing to comply with all study requirements.

You will be asked to complete surveys in the available language throughout the study.

2 Maternal vaccination allocation

You may be allocated to receive a maternal vaccine during pregnancy. The vaccine is called Abrysvo, which is a vaccine against respiratory syncytial virus (a common virus that can cause breathing problems in infants).

If allocated, the vaccine will be given as an injection into the muscle.

Not all participants will receive the maternal vaccine, as allocation depends on the study design.

3 Birth of your infant

After your baby is born, your infant will be enrolled in the study.

Informed consent for your infant’s participation will be confirmed. This consent must be provided by you as the mother, and may also require consent from the other legal representative or guardian, depending on local regulations.

4 Infant treatment allocation

Your infant may be allocated to receive a monoclonal antibody (a type of medication that helps protect against infection). The medication is called nirsevimab, marketed as Beyfortus.

The monoclonal antibody may be given at different time points depending on the study allocation.

The medication will be administered as an injection into the muscle.

The dosage will be either 50 mg or 100 mg, depending on your infant’s weight and age at the time of administration.

5 First RSV season monitoring

Your infant will be monitored during the first RSV season after birth. RSV season refers to the time of year when respiratory syncytial virus is most common in the community.

If your infant develops symptoms of a respiratory tract infection (such as cough, difficulty breathing, or fever), testing for RSV may be performed.

You will need to report any respiratory symptoms your infant experiences during this period.

6 Infant monoclonal antibody at 4 months

Some infants may be allocated to receive an additional dose of the monoclonal antibody (nirsevimab) at 4 months of age.

This will be given as an injection into the muscle.

The dosage will be either 50 mg or 100 mg, depending on your infant’s weight at that time.

7 Follow-up until 12 months of age

Your infant will be followed until 12 months of age.

During this time, monitoring will continue for any symptomatic RSV respiratory tract infection. This means any breathing-related illness caused by the respiratory syncytial virus that is confirmed by an approved test.

You will be asked to complete participant surveys at scheduled intervals throughout this period.

You will need to report any respiratory symptoms or illnesses your infant experiences.

8 Study completion

The study will be complete when your infant reaches 12 months of age.

All required surveys and assessments will need to be completed by this time.

The overall study is expected to continue enrolling participants until 2029, but your individual participation will end when your infant turns 12 months old.

Who Can Join the Study?

You must be a pregnant woman who is carrying a baby
You must be between 24 weeks and 36 weeks and 6 days pregnant, which means you are in the middle to later part of your pregnancy
You must be older than the legal age of consent in your country, which is the age when you can legally make decisions for yourself
You must be willing and able to sign a form showing you agree to take part in the study, which is called informed consent
You must be willing and able to follow all the requirements of the study
You must be able to read and fill out questionnaires in a language that is offered in the study
You must be willing to receive a maternal vaccine during your pregnancy if the study assigns you to receive it, which is a medicine given to pregnant mothers to help protect their babies
You must be willing for your baby to receive an infant monoclonal antibody if the study assigns your baby to receive it, which is a type of medicine that helps protect babies from infection
Your baby must be born alive to you as the mother enrolled in the study
For your baby to participate, you as the mother must agree, and the other parent or legal guardian must also agree if this is required by local rules

Who Cannot Join the Study?

No exclusion criteria have been provided in the available study information for this clinical trial.

Where you can join this trial?

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Other Sites

Site Name	City	Country
Diakonessenhuis Stichting	Utrecht	The Netherlands
Wdpeyxpjvz Clzyfpmdr Htopzpwo	Utrecht	The Netherlands
Ulqlfzfnbf Ot Anjdbwm	Edegem	Belgium

Trial status

Country	Status	Recruitment Start
Belgium	Not yet recruiting	01.09.2025
The Netherlands	Not yet recruiting	01.09.2025

Trial locations

MV is a maternal vaccine given to pregnant women to help protect their babies from RSV (a common respiratory virus) after birth. The vaccine works by helping the mother’s body create protective antibodies that pass to the baby before birth.

Infant mAb is a monoclonal antibody treatment given directly to infants. This medication provides immediate protection against RSV by giving the baby ready-made antibodies that fight the virus. It is given to babies during their first RSV season to help prevent serious respiratory infections.

Investigated diseases:

Respiratory syncytial virus infection

Respiratory Syncytial Virus Infection – Respiratory Syncytial Virus infection is a common viral illness that affects the breathing passages, particularly in infants and young children. The virus enters the body through the nose, mouth, or eyes and begins to multiply in the upper airways. As the infection progresses, it can spread to the lower respiratory tract, affecting the small airways in the lungs called bronchioles. This can lead to inflammation and swelling of these airways, making it difficult for air to pass through. Symptoms typically include runny nose, cough, sneezing, fever, and wheezing. In infants, the infection may cause difficulty breathing, decreased appetite, and irritability.

Trial ID:

2025-522194-11-00

NCT ID:

NCT07041190

Trial Phase:

Therapeutic confirmatory (Phase III)

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Study of RSV vaccine and nirsevimab combination to prevent RSV infection in infants up to 12 months of age

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