Is the RSV (Respiratory Syncytial Virus) vaccine recommended during pregnancy?

RSV Vaccination During Pregnancy

The CDC recommends maternal RSV vaccination for pregnant persons as a one-time dose at 32-36 weeks' gestation using seasonal administration (September-January in most of the continental United States) to prevent RSV-associated lower respiratory tract infection in infants aged <6 months. 1

Recommendation Details

The Advisory Committee on Immunization Practices (ACIP) and CDC specifically recommend:

• A single 0.5 mL intramuscular dose of RSVpreF vaccine (Abrysvo, Pfizer Inc.)
• Administration during 32 weeks 0 days to 36 weeks 6 days of gestation
• Seasonal timing: September through January in most of the continental United States
• Goal: Prevention of RSV-associated lower respiratory tract infection (LRTI) in infants

Protection Strategy Options

There are two recommended approaches to protect infants against RSV:

1. Maternal RSVpreF vaccination during pregnancy
2. Nirsevimab administration to the infant after birth

Either approach is recommended, but both are not needed for most infants 1, 2. The choice between these options should be based on:

• Timing of birth relative to RSV season
• Gestational age at birth
• Maternal vaccination status
• Infant risk factors

Efficacy of Maternal RSV Vaccination

Maternal RSV vaccination has demonstrated effectiveness in preventing RSV-associated lower respiratory tract disease in infants:

• Reduces risk of any medically assessed RSV-associated LRTI by 65.5% in infants from birth to 6 months 3
• Reduces risk of severe medically assessed RSV-associated LRTI by 69.0% 3
• Provides immediate protection after birth 1
• Generates a polyclonal immune response that may be more resistant to potential mutations in the RSV F protein 1

Safety Considerations

The FDA has identified potential safety concerns that should be discussed with patients:

• Preterm birth: More preterm births (<37 weeks' gestation) were observed among RSVpreF vaccine recipients than placebo recipients, although differences were not statistically significant in the approved dosing interval (32-36 weeks) 1
• Hypertensive disorders of pregnancy: More cases were observed among RSVpreF vaccine recipients, though differences were not statistically significant 1

The FDA determined that when administered during 32-36 weeks' gestation, the benefits of preventing RSV-associated LRTI in infants outweigh these potential risks 1.

When Nirsevimab Should Be Used Instead

Nirsevimab is recommended for infants in the following scenarios:

• Infants born outside of RSV season (April-September)
• Infants born <14 days after maternal RSVpreF vaccination
• Infants born at <34 weeks' gestation
• Infants whose mothers did not receive RSVpreF vaccine
• Infants whose mother's receipt of RSVpreF vaccine is unknown 1

Nirsevimab may also be considered for infants born to vaccinated mothers in specific circumstances:

• Infants born to immunocompromised mothers
• Infants born to mothers with conditions associated with reduced transplacental antibody transfer
• Infants who might have experienced loss of maternal antibodies
• Infants at substantially increased risk for severe RSV disease 1

Implementation Considerations

• Timing is crucial: Administering maternal RSVpreF vaccine starting in September (1-2 months before the anticipated start of RSV season) and continuing through January maximizes cost-effectiveness 1
• Co-administration: RSVpreF vaccine can be administered with other recommended vaccines for pregnant persons (Tdap, influenza, COVID-19) without regard to timing 1
• Regional variations: In regions with different RSV seasonality patterns (Alaska, southern Florida, Hawaii, etc.), providers should follow local guidance on timing 1
• Provider recommendation matters: Studies show that provider recommendation significantly increases vaccination rates - 55.8% of infants were protected by maternal RSV vaccine, nirsevimab, or both in the 2023-24 season 4

Common Pitfalls and Caveats

• Timing window is strict: Vaccination must occur between 32-36 weeks' gestation - not earlier or later
• Subsequent pregnancies: No data are currently available on efficacy of first lifetime dose to protect infants born after subsequent pregnancies or safety of additional doses during subsequent pregnancies 1
• Vaccine hesitancy: Some pregnant women express concerns about vaccine safety and effectiveness, particularly following COVID-19 vaccination experiences 5
• Transplacental transfer time: At least 14 days are needed after maternal vaccination for development and transplacental transfer of maternal antibodies to protect the infant 1

In conclusion, RSV vaccination during pregnancy is recommended as part of a comprehensive strategy to protect infants against RSV-associated lower respiratory tract disease, with specific timing and administration guidelines to maximize benefits while minimizing potential risks.