What are the recommendations for administering the Respiratory Syncytial Virus (RSV) vaccine to a pregnant woman?

RSV Vaccination During Pregnancy

Administer the Pfizer RSVpreF vaccine to pregnant persons at 32 weeks 0 days through 36 weeks 6 days of gestation during September through January in most of the continental United States. 1

Timing Algorithm

Gestational Age Window

• Vaccinate between 32+0 and 36+6 weeks' gestation to optimize infant protection while minimizing potential preterm birth risk 1, 2, 3
• This narrower window (compared to the trial's 24-36 week dosing) was selected because preterm birth rates were 4.2% in the vaccine group versus 3.7% in placebo when administered at 32-36 weeks, compared to 5.7% versus 4.7% when given at 24-36 weeks 1, 3
• Most preterm births in the approved interval occurred at 36 weeks' gestation (72% of vaccine group preterm births), and these differences were not statistically significant 3

Seasonal Timing

• Administer during September through January in most of the continental United States 1, 2
• Begin vaccination 1-2 months before anticipated RSV season onset and continue through 2-3 months before anticipated season end 2, 4
• For Alaska, southern Florida, Guam, Hawaii, Puerto Rico, U.S.-affiliated Pacific Islands, and U.S. Virgin Islands, follow local guidance due to different RSV seasonality patterns 2, 4

Protection Characteristics

• At least 14 days are required after maternal vaccination for adequate antibody development and transplacental transfer to protect the infant 2, 4
• Protection likely wanes after approximately 3 months, similar to other maternal vaccines 4
• This timing protects infants during their most vulnerable period, as RSV causes 58,000-80,000 annual hospitalizations in children under 5 years, with peak rates at 2-3 months of life 3, 5

Co-Administration with Other Vaccines

• RSV vaccine can be administered simultaneously with Tdap, influenza, and COVID-19 vaccines at different anatomic sites on the same day 2, 3, 4

Safety Profile

• No statistically significant differences were observed between vaccine and placebo groups for preterm birth, low birthweight, or neonatal jaundice outcomes 1, 2, 4
• The FDA determined that benefits outweigh risks when administered at 32-36 weeks' gestation 3
• Local injection-site reactions are more common with the vaccine (40.7% vs 9.9% with placebo), but most are mild to moderate 6
• No cases of Guillain-Barré syndrome or other inflammatory neurologic events were reported in pregnancy trials, though such events occurred in adults aged ≥60 years receiving the same vaccine 1

Critical Caveats

Single Lifetime Dose Recommendation

• Current recommendations are for a single lifetime dose only 2, 4
• No data are available on efficacy or safety of additional doses during subsequent pregnancies 2, 4, 7

Alternative: Nirsevimab for Infants

• Either maternal RSV vaccination OR infant nirsevimab is recommended, but both are not needed for most infants 2, 3, 4
• Exception: All infants born at <34 weeks' gestation should receive nirsevimab regardless of maternal vaccination status 2, 3, 4
• Nirsevimab is also recommended for infants whose mothers did not receive RSV vaccine, whose mother's vaccination status is unknown, or who were born <14 days after maternal vaccination 4

Common Pitfalls to Avoid

• Do not vaccinate before 32 weeks' gestation due to the slightly higher preterm birth signal observed in earlier vaccination windows 1, 3
• Do not vaccinate after 36 weeks 6 days' gestation as this falls outside the approved and studied interval 1, 4
• Do not vaccinate outside of RSV season (September-January in most of US) as protection wanes after 3 months and would not cover the infant's vulnerable period 1, 2
• Do not administer both maternal vaccine and infant nirsevimab to most infants, as this represents unnecessary duplication 2, 3, 4