- Article
- Source: Campus Sanofi
- Nov 7, 2025
Nirsevimab FAQs
Nirsevimab is a long-acting human monoclonal antibody designed to prevent respiratory syncytial virus (RSV) infections in infants and young children.
Key Features:
Single-dose protection - Provides protection throughout the entire RSV season with just one injection
Broad population coverage - Designed for ALL infants:
- Healthy term and late preterm infants
- Preterm infants
- Infants with chronic lung disease (CLD) or congenital heart disease (CHD)
Administration & Dosing:
- Route: Intramuscular injection
- Dosing:
- 50 mg for infants weighing < 5 kg
- 100 mg for infants weighing ≥ 5 kg
- Timing: Administered before or at the start of RSV season, regardless of birth timing
Frequently Asked Questions (FAQs):
RSV Immunization: Target Patient Population
The American Academy of Pediatrics (AAP) recommends RSV immunization with nirsevimab for:
- infants <8 months of age born during or entering their first RSV season if:
- pregnant parent did not receive RSVpreF vaccine during this pregnancy,
- pregnant parent’s RSVpreF vaccination status is unknown, or
- infant was born <14 days after the pregnant parent’s RSVpreF vaccination
- pregnant parent did not receive RSVpreF vaccine during this pregnancy,
Infants and children 8 through 19 months of age at high risk of severe RSV disease and entering their second RSV season, regardless of the RSV vaccination status of the pregnant parent or the child’s prior receipt of nirsevimab when <8 months of age. High-risk criteria include the following:
- Children with chronic lung disease of prematurity who required medical support (chronic corticosteroid therapy, diuretic therapy, or supplemental oxygen) at any time during the 6-month period before the start of the second RSV season
- Children with severe immunocompromise
- Children with cystic fibrosis have either:
- manifestations of severe lung disease (previous hospitalization for pulmonary exacerbation in the first year of life or abnormalities on chest imaging that persist when stable), or
- weight-for-length that is less than the 10th percentile
Yes. Most hospitalizations for RSV occur in otherwise healthy infants born at term. RSV is a leading cause of hospitalizations in all infants less than 12 months worldwide.
Yes, Nirsevimab has been approved for use in preterm infants
Duration of protection:
Protection from RSV immunization is expected to last at least 5 months, about the length of an RSV season.
Administration:
The baby first RSV season is the period of greatest risk of severe disease, because their immune systems are still maturing and their airways are still developing. Giving them antibodies passively by injection can help protect them during this time.
The recommended interval between the last dose of palivizumab and a dose of Nirsevimab is 1 month.
Avoid using two 50 mg nirsevimab doses for infants weighing ≥5 kilograms because 50 mg doses should be reserved for smaller infants who are at increased risk for severe RSV illness because of their smaller airways.
No, Nirsevimab 100 mg doses are approved for single use. They are intended for ONE patient for ONE injection.
Yes. Simultaneous administration of RSV immunization with age-appropriate vaccines is recommended.
Like routine childhood vaccines, mild illness – with or without fever – should not be used as a reason to delay administration of Nirsevimab.
Yes. Optimal timing for administration is within 1 week after birth during the RSV season. Administering RSV immunization through the end of the season is important because the risk of severe disease is highest during the first few months of life.
If a half dose is mistakenly given, another half dose should be administered as soon as possible.
- It is recommended that infants born shortly before and during the RSV season receive RSV immunization within the first week of life, including in hospital setting.
- Infants with prolonged birth hospitalizations because of prematurity or other causes should receive RSV immunization shortly before or promptly after discharge
Yes. Healthy infants born at the end of their first RSV season who did NOT receive RSV immunization may receive one dose of RSV immunization if they are < 8 months of age entering their second RSV season.
Prior infection should generally not be used to determine an infant’s eligibility for RSV immunization.
Nirsevimab comes in prefilled syringes. Anyone who can administer injections can administer nirsevimab.
Safety Profile:
The possible side effects: Injection site reactions, some pain, swelling and redness where babies are injected, which is a typical side effect of immunizations and vaccines.
Nirsevimab is contraindicated in infants and young children with a history of serious hypersensitivity reactions, including anaphylaxis, to Nirsevimab to any of their components.
Supply:
A shortage of nirsevimab is not expected this coming season.
MAT-KW-2500556/V1/November2025