Which Respiratory Syncytial Virus (RSV) vaccine is given to a pregnant woman?

RSV Vaccination in Pregnancy

The RSVpreF (bivalent RSV prefusion F protein-based) vaccine is the RSV vaccine given to pregnant women, administered as a single 0.5 mL intramuscular dose between 32 weeks 0 days and 36 weeks 6 days of gestation. 1, 2, 3

Specific Vaccine Product and Dosing

• The vaccine contains 120 μg of bivalent RSV prefusion F protein 4, 5
• It is administered as a single intramuscular injection during the specified gestational window 1, 3
• This is currently recommended as a single lifetime dose, with no data available on safety or efficacy of repeat dosing in subsequent pregnancies 1, 4

Optimal Timing for Administration

• Administer between 32 weeks 0 days and 36 weeks 6 days of gestation 1, 2, 3
• Seasonal timing matters: give during September through January in most of the continental United States 1, 3
• At least 14 days are required after vaccination for adequate antibody development and transplacental transfer to protect the infant 1, 2, 3
• For regions with different RSV seasonality (Alaska, southern Florida, Guam, Hawaii, Puerto Rico, U.S.-affiliated Pacific Islands, and U.S. Virgin Islands), follow local guidance 1, 3

Efficacy Data

• The vaccine demonstrated 81.8% efficacy against medically attended severe RSV-associated lower respiratory tract illness in infants within 90 days of birth 5
• Efficacy was 69.4% against severe disease within 180 days of birth 5
• Protection likely wanes after approximately 3 months, similar to other maternal vaccines 1, 3
• Neutralizing antibody titers in mothers increased 12.7-14.9-fold against RSV-A and 10.6-13.2-fold against RSV-B one month post-vaccination 6

Safety Profile and Important Caveat

• No statistically significant differences were observed between vaccine and placebo groups for low birthweight or neonatal jaundice 1, 3
• Critical safety concern: One trial (RSVPreF3-Mat by GSK) showed a higher risk of preterm birth in the vaccine group (6.8%) compared to placebo (4.9%), with relative risk of 1.37 7
• The Pfizer RSVpreF vaccine trial did not detect safety signals and showed similar adverse event rates between vaccine and placebo groups 5
• Local injection-site reactions are more common with vaccine (approximately 40%) compared to placebo 8, 5

Co-administration with Other Vaccines

• RSV vaccine can be administered simultaneously with other recommended vaccines for pregnant persons (Tdap, influenza, COVID-19) at different anatomic sites on the same day 1, 3

Alternative Strategy: Infant Nirsevimab

• Either maternal RSV vaccination OR infant nirsevimab is recommended, but both are not needed for most infants 1, 2, 3
• Nirsevimab is recommended for infants whose mothers did not receive RSV vaccine, whose vaccination status is unknown, or who were born <14 days after maternal vaccination 1, 2
• All infants born at <34 weeks gestation should receive nirsevimab regardless of maternal vaccination status 1, 2, 3
• Infants born to immunocompromised mothers require nirsevimab regardless of maternal vaccination status 2

Clinical Decision Algorithm

1. Confirm gestational age is 32 weeks 0 days to 36 weeks 6 days 1
2. Verify current month is within seasonal administration period (September-January in most of US) 1, 3
3. Assess for contraindications: severe allergic reaction (anaphylaxis) to any vaccine component, or moderate/severe acute illness 2
4. Discuss relative advantages of maternal vaccination versus infant nirsevimab with the patient, including the preterm birth signal observed in one trial 1, 7
5. If proceeding with vaccination, document administration and expected delivery date to determine if infant will need nirsevimab based on timing of birth relative to vaccination 1
6. If beyond 36 weeks 6 days gestation, plan for infant nirsevimab administration after delivery instead 2