What are the options for RSV (Respiratory Syncytial Virus) prevention in pregnant individuals who cannot receive the RSV vaccine before 36 weeks of gestation?

RSV Protection Options When Maternal Vaccination Cannot Be Given Before 36 Weeks

If a pregnant person cannot receive the RSV vaccine before 36 weeks gestation, the infant should receive nirsevimab (monoclonal antibody) after birth to prevent RSV-associated lower respiratory tract disease. 1

Primary Recommendation: Infant Nirsevimab Administration

• Nirsevimab is recommended for all infants whose mothers did not receive RSVpreF vaccine during pregnancy, including those who could not be vaccinated before 36 weeks. 1, 2
• The monoclonal antibody should be administered to infants <8 months who are born during or entering their first RSV season. 1
• Nirsevimab provides direct antibody protection without relying on transplacental transfer, making it the appropriate alternative when maternal vaccination timing is missed. 1

Timing Considerations for Late Pregnancy Scenarios

If Currently Beyond 36 Weeks 6 Days Gestation:

• Do NOT administer maternal RSV vaccine - the approved window has closed and vaccination is only indicated between 32 weeks 0 days and 36 weeks 6 days. 1, 3
• Plan for infant nirsevimab administration after delivery instead. 1, 2

If Currently Before 32 Weeks But Will Reach 36 Weeks Outside RSV Season:

• Maternal vaccination should only occur during September-January in most of the continental United States (seasonal administration). 1, 4
• If the 32-36 week window falls outside this seasonal period, skip maternal vaccination and plan for infant nirsevimab at the onset of RSV season if the infant will be <8 months old. 1, 4

Critical Timing Requirements for Maternal Vaccination

• At least 14 days are required after maternal vaccination for adequate antibody development and transplacental transfer to protect the infant. 1, 2
• Infants born <14 days after maternal vaccination should receive nirsevimab regardless of maternal vaccination status. 2, 4
• The earliest an infant can be considered protected from maternal vaccination is if born at 34 weeks' gestation or later when vaccine is given at 32 weeks. 2

Special Populations Requiring Nirsevimab Regardless

Certain infants need nirsevimab even if maternal vaccination occurred:

• All infants born at <34 weeks' gestation (preterm infants require nirsevimab regardless of maternal vaccination status). 2, 4
• Infants whose mothers are immunocompromised (reduced antibody production or transfer). 1, 2
• Infants with high-risk medical conditions. 2

Advantages of Nirsevimab as Alternative Strategy

• Protection may wane more slowly than maternal vaccine-derived antibodies, which typically decline after 3 months. 1, 4
• Assures direct receipt of antibodies rather than relying on transplacental transfer. 1
• No risk for adverse pregnancy outcomes (unlike the potential preterm birth warning associated with maternal vaccination). 1, 3
• Does not require the infant to be born during a specific timeframe relative to vaccination. 1

Common Pitfall to Avoid

• Do NOT administer both maternal RSV vaccine and infant nirsevimab - both products are not needed for most infants. 1, 2
• The only exceptions are infants born <34 weeks' gestation or those with specific high-risk conditions. 2, 4

Practical Implementation

• Nirsevimab availability should be confirmed, as there were supply concerns during the 2023-24 RSV season. 1
• The infant will require an injection, which should be discussed with parents as part of shared decision-making. 1
• Document maternal vaccination status clearly in medical records to ensure appropriate infant management. 2