What are the guidelines for Respiratory Syncytial Virus (RSV) vaccination in neonates?

RSV Protection in Neonates

All neonates should receive RSV protection through either maternal RSVpreF vaccination during pregnancy (administered at 32-36 weeks' gestation) or nirsevimab monoclonal antibody administration after birth, but both are not needed for most infants. 1

Maternal Vaccination Strategy

Maternal RSVpreF vaccine (Abrysvo) is FDA-approved as a single 0.5 mL intramuscular dose given between 32 weeks 0 days and 36 weeks 6 days of gestation to prevent RSV-associated lower respiratory tract disease in infants under 6 months of age. 1

Timing and Seasonal Administration

• Administer during September through January in most of the continental United States (timing varies by region based on local RSV seasonality) 1
• At least 14 days are required after maternal vaccination for adequate antibody development and transplacental transfer to protect the infant 1
• The earliest an infant can be considered protected is if born at 34 weeks' gestation or later (when vaccine given at the earliest recommended time of 32 weeks) 1

Advantages of Maternal Vaccination

• Provides immediate protection after birth 1
• Generates a polyclonal immune response that may be more resistant to potential RSV F protein mutations compared to monoclonal antibodies 1

Important Safety Considerations

• FDA has labeled a potential risk for preterm birth as a warning, though clinical trial differences were not statistically significant 1
• More hypertensive disorders of pregnancy were observed in vaccine recipients versus placebo, though not statistically significant 1
• The vaccine is approved for 32-36 weeks specifically to avoid potential preterm birth risk at <32 weeks' gestation, which carries increased morbidity and mortality 1

Nirsevimab (Monoclonal Antibody) Strategy

Nirsevimab is recommended for infants <8 months born during or entering their first RSV season in the following situations: 1

Mandatory Indications for Nirsevimab

• All infants born at <34 weeks' gestation (regardless of maternal vaccination status) 1
• Infants whose mothers did not receive RSVpreF vaccine 1
• Infants whose mother's vaccination status is unknown 1
• Infants born <14 days after maternal RSVpreF vaccination (insufficient time for antibody transfer) 1
• Infants born outside RSV season (April-September) who are <8 months at RSV season onset 1

Optional Nirsevimab (Clinical Judgment Required)

Nirsevimab may be considered for infants born to vaccinated mothers in rare circumstances when incremental benefit is warranted: 1

• Infants born to immunocompromised mothers who may not have mounted adequate immune response 1
• Infants born to mothers with conditions causing reduced transplacental antibody transfer (e.g., HIV infection) 1
• Infants who experienced loss of maternal antibodies (e.g., after cardiopulmonary bypass or ECMO) 1
• Infants with substantially increased risk for severe RSV disease (hemodynamically significant congenital heart disease, intensive care admission requiring oxygen at discharge) 1

High-Risk Infants in Second RSV Season

• Infants and children aged 8-19 months at increased risk for severe RSV disease entering their second RSV season should receive nirsevimab regardless of maternal vaccination 1

Critical Clinical Pitfalls

Do Not Routinely Give Both Products

Nirsevimab is NOT needed for most infants <8 months whose mother received RSVpreF vaccine ≥14 days before birth. 1 Both products provide protection, and dual administration is unnecessary for most infants.

Palivizumab (Synagis) Considerations

• Palivizumab requires monthly dosing at 15 mg/kg throughout RSV season 2
• Indicated for specific high-risk populations: premature infants ≤35 weeks' gestation who are ≤6 months at RSV season start, infants with bronchopulmonary dysplasia ≤24 months requiring treatment within 6 months, and infants with hemodynamically significant congenital heart disease ≤24 months 2
• Palivizumab has largely been superseded by nirsevimab due to cost and need for monthly administration 3

Contraindications

• RSV vaccines are contraindicated in persons with history of severe allergic reaction (anaphylaxis) to any vaccine component 1
• Delay vaccination for moderate or severe acute illness with or without fever 1

Algorithm for Clinical Decision-Making

For pregnant patients at 32-36 weeks' gestation during RSV season (September-January):

1. Offer maternal RSVpreF vaccination unless contraindicated
2. If declined or contraindicated, plan for infant nirsevimab after delivery

For neonates after birth:

1. If mother received RSVpreF ≥14 days before birth AND infant born ≥34 weeks' gestation → No nirsevimab needed for most infants
2. If mother received RSVpreF <14 days before birth OR infant born <34 weeks → Give nirsevimab
3. If maternal vaccination status unknown or not given → Give nirsevimab
4. If infant has high-risk conditions (immunocompromised mother, congenital heart disease, etc.) → Consider nirsevimab even if maternal vaccine criteria met