RSV Vaccination During Pregnancy Improves Infant Outcomes

Does administration of the respiratory syncytial virus (RSV) vaccine during pregnancy improve infant outcomes?

Maternal RSV vaccination during pregnancy leads to fewer infant hospitalizations with laboratory-confirmed RSV disease compared with placebo.¹ (Strength of Recommendation [SOR]: A, consistent, good-quality patient-oriented evidence.) Maternal RSV vaccination during pregnancy likely makes little to no difference in intrauterine growth restriction or congenital abnormalities compared with placebo. (SOR: B, inconsistent or limited-quality patient-oriented evidence.) There is also likely little to no difference in rates of preterm labor, stillbirth, infant death, or maternal death, although the quality of this evidence is low. (SOR: B, inconsistent or limited-quality patient-oriented evidence.)

RSV is a clinically significant disease that leads to 2.1 million outpatient visits and 58,000 to 80,000 hospitalizations among children younger than 5 years in the United States annually.² RSV most notably affects younger infants, with almost one-half of affected infants younger than 6 months.³

The significant impact of RSV infection in neonates has led to the development and distribution of a maternal RSV vaccine given during pregnancy. Additional available maternal vaccines during pregnancy intended to protect newborns include tetanus, diphtheria, pertussis; influenza; and COVID-19.⁴ Maternal RSV vaccination during pregnancy increases naturally acquired RSV immunoglobulin (Ig) G, which transfers to the infant via the placenta and provides passive immunity, reducing infant RSV disease burden.⁵ This transplacental IgG transfer is most efficient in the third trimester of pregnancy. Serologic studies have reported that maternally acquired IgG antibodies are present in the newborn up to 4 months after birth.⁶ The authors of this review sought to determine whether maternal RSV vaccination prevents subsequent infant hospitalization with RSV, as well as whether maternal RSV vaccination during pregnancy affects rates of intrauterine growth restriction, stillbirth, maternal death, preterm birth, congenital abnormalities, and infant death.¹

This Cochrane review included six randomized controlled trials (RCT) with 17,991 pregnant patients up to age 49 years.¹ Study duration was 90 to 365 days, and most studies were conducted in the United States. The timing of RSV vaccination varied from 24 to 36 weeks' gestation. Of note, all studies were funded by RSV vaccine manufacturers. The primary outcome was infant hospitalizations with laboratory-confirmed RSV disease before 1 year of life. Secondary outcomes included intrauterine growth restriction, stillbirth, maternal death, preterm birth, congenital abnormalities noted in the first year of life, and infant death.

High-certainty evidence showed that maternal RSV vaccination decreased infant hospitalization with laboratory-confirmed RSV disease compared with placebo (risk ratio = 0.50; 95% CI, 0.31–0.82; four studies; n = 12,216; number needed to treat = 90 [95% CI, 65–249]).¹ Moderate-certainty evidence showed that maternal RSV vaccination had little to no effect on intrauterine growth restriction compared with placebo. Maternal RSV vaccination also made no difference on rates of stillbirth or maternal death.

There is likely little to no difference in rates of preterm labor, stillbirth, infant death, or maternal death between maternal RSV vaccination and placebo administration, although the quality of this evidence is low.¹

The Centers for Disease Control and Prevention Advisory Committee on Immunization Practices recommends seasonal maternal vaccination (September–January) with the Abrysvo RSV vaccine between 32 weeks 0 days' and 36 weeks 6 days' gestation.⁷ The American Academy of Family Physicians, American College of Obstetricians and Gynecologists, and American Academy of Pediatrics also endorse these recommendations.^8–10