Should RSV vaccination be given to the pregnant mother in the third trimester, or should RSV prophylaxis (nirsevimab) be administered to the newborn at birth?

RSV Prevention: Maternal Vaccination vs. Infant Nirsevimab

Either maternal RSVpreF vaccination during pregnancy (32-36 weeks) or nirsevimab administration to the infant at birth is acceptable, but based on the most recent head-to-head comparative data, nirsevimab at birth demonstrates superior effectiveness in preventing RSV-related hospitalizations and severe outcomes compared to maternal vaccination.

Current CDC Recommendations

The 2023 ACIP guidelines establish that both products are not needed for most infants 1. Providers should discuss the relative advantages and disadvantages of both options with pregnant patients and consider patient preferences when determining which strategy to use 1.

Key Decision Points

Choose Nirsevimab for the Infant When:

• Infant born <34 weeks gestation (always give nirsevimab regardless of maternal vaccination) 1
• Infant born <14 days after maternal vaccination (insufficient time for antibody transfer) 1
• Mother is immunocompromised (may not mount adequate immune response to vaccine) 1
• Mother has conditions affecting transplacental antibody transfer (e.g., HIV infection) 1
• Infant born outside RSV season (April-September births should receive nirsevimab at onset of RSV season if <8 months old) 1
• Mother's vaccination status unknown 1

Choose Maternal RSVpreF Vaccination When:

• Pregnancy at 32-36 weeks during September-January 1
• Anticipated delivery ≥14 days after vaccination 1
• Term pregnancy expected (≥34 weeks) 1
• Patient preference to avoid infant injection 1

Comparative Effectiveness: Recent Evidence

The most recent and highest quality comparative data from France (2024-2025 RSV season) provides critical insights:

In a population-based cohort of 42,560 matched infants 2:

• Nirsevimab reduced RSV hospitalization risk by 26% compared to maternal RSVpreF vaccine (adjusted HR 0.74,95% CI 0.61-0.88)
• Nirsevimab reduced PICU admission by 42% (adjusted HR 0.58,95% CI 0.42-0.80)
• Nirsevimab reduced need for ventilator support by 43% (adjusted HR 0.57,95% CI 0.40-0.81)
• Nirsevimab reduced need for oxygen therapy by 44% (adjusted HR 0.56,95% CI 0.38-0.81)

A second French study of 164,140 infants 3 confirmed:

• Nirsevimab reduced odds of RSV hospitalization by 22% compared to maternal vaccine (OR 0.78,95% CI 0.70-0.86)
• Critical timing finding: When maternal vaccine was given ≥8 weeks before delivery, there was no statistical difference in effectiveness compared to nirsevimab (OR 1.01,95% CI 0.77-1.32)

Relative Advantages and Disadvantages

Maternal RSVpreF Vaccination

Advantages:

• Provides protection immediately after birth 1
• Polyclonal immune response may be more resistant to viral mutations 1
• No infant injection required 1

Disadvantages:

• Potential risk for preterm birth and hypertensive disorders of pregnancy 1
• Protection wanes after 3 months 1
• Reduced effectiveness if inadequate antibody production or transfer 1
• Requires ≥14 days before delivery for adequate antibody transfer 1

Nirsevimab (Infant Administration)

Advantages:

• No risk for adverse pregnancy outcomes 1
• Protection may wane more slowly than maternal vaccine 1
• Assures direct receipt of antibodies (no reliance on transplacental transfer) 1
• Superior effectiveness demonstrated in real-world data 2, 3
• Duration of protection extends through 5 months 4

Disadvantages:

• Requires infant injection 1
• Potentially limited availability during initial rollout 1

Clinical Algorithm

For infants born during RSV season (October-March):

1. If mother received RSVpreF vaccine ≥14 days before delivery AND infant born ≥34 weeks gestation:

   • Nirsevimab NOT needed for most infants 1
   • Consider nirsevimab only in special circumstances (maternal immunocompromise, HIV, conditions requiring cardiopulmonary bypass) 1

2. If mother did NOT receive vaccine OR vaccine given <14 days before delivery OR infant born <34 weeks:

   • Give nirsevimab 1

3. If mother's vaccination status unknown:

   • Give nirsevimab 1

For infants born outside RSV season (April-September):

• Give nirsevimab at onset of RSV season if infant <8 months old 1

Important Caveats

Timing Considerations

• Maternal vaccination should occur at 32-36 weeks gestation during September-January only 1
• At least 14 days needed after maternal vaccination for adequate antibody development and transfer 1
• Nirsevimab should be given within 1 week of birth for infants born during RSV season 5

Safety Signal

The maternal vaccine has a potential risk for preterm birth that remains under surveillance 1. This safety concern, combined with the superior effectiveness data for nirsevimab 2, 3, supports a preference for infant nirsevimab when both options are available and acceptable to the family.

No Direct Comparison Trials

The CDC notes that no data are available directly comparing efficacy of nirsevimab and maternal RSVpreF vaccine 1. However, the recent French population-based studies 2, 3 provide the best available real-world comparative effectiveness data, consistently showing superior outcomes with nirsevimab.

Cost-Effectiveness Considerations

Nirsevimab for first RSV season is estimated at $102,811 per QALY 5. Maternal vaccination may be more cost-effective when administered early in the RSV season (October-December) 6, but this must be balanced against the superior clinical effectiveness of nirsevimab demonstrated in recent comparative studies 2, 3.

Bottom Line

Given the most recent comparative effectiveness data showing superior protection with nirsevimab, particularly for severe outcomes requiring PICU admission and ventilator support, nirsevimab at birth is the preferred strategy when both options are available 2, 3. However, maternal vaccination remains an acceptable alternative, particularly when given ≥8 weeks before delivery 3, and should be offered when nirsevimab availability is limited or patient preference favors avoiding infant injection.