RSV Protection for Infants: Maternal Vaccine and Nirsevimab, 2023–24 (MMWR)

Summary

• Already known: respiratory syncytial virus (RSV) is the most common cause of hospitalization among U.S. infants. 2023–24 was the first season with a recommended maternal RSV vaccine or an RSV antibody for infants, nirsevimab.
• This report: in a CDC survey, 33% of eligible pregnant women got an RSV vaccine, 45% of infants got nirsevimab, and 56% of infants were protected by one or both. A provider's recommendation was linked to higher coverage.
• Implication: stronger efforts to put provider RSV recommendations into practice are needed.

The recommendations

To protect infants from RSV lower respiratory tract disease, the Advisory Committee on Immunization Practices recommends either:

• a single RSV vaccine dose for pregnant people at 32–36 weeks' gestation, given September–January; or
• nirsevimab for infants under 8 months born during or entering their first RSV season (October–March in most of the continental U.S.).

Most infants don't need both. Infants under 3 months have the highest RSV hospitalization rates.

The survey

CDC ran an internet panel survey on March 26–April 11, 2024, of women 18–49 who had been pregnant since August 1, 2023: 2,266 of 2,473 eligible (91.6%) completed it.

Who got immunized

• Maternal vaccine coverage was higher with private or military insurance (38.9% vs 28.0% public), at or above poverty (35.0% vs 26.4%), with more than a college degree (50.1%), and — most strikingly — with a provider recommendation (56.7% vs 1.9%). Most vaccinated women (54.1%) got it at an OB-GYN's office.
• Nirsevimab coverage was higher when mothers were employed (48.5% vs 38.7%) and with a provider recommendation (58.7% vs 28.3%).

Why not

Main reasons for not getting maternal RSV vaccination (top) and for definitely or probably not getting nirsevimab for an infant (bottom). CDC.

Preferences

Of women who had given birth or were pregnant: 38.1% preferred the maternal vaccine, 27.8% nirsevimab, 21.3% had no preference, and 12.8% wanted neither. Those preferring the vaccine most often thought it safer (47.8%) or worried about too many shots for the baby (30.2%); those preferring nirsevimab most often thought it more effective (43.6%).

Discussion

• A hard first season: timing of recommendations and supply, different timing for the two products, complex guidance, little time to raise awareness, cost and reimbursement, access, and safety concerns likely held coverage down. Nirsevimab was in short supply, and many OB-GYN offices lacked vaccine — especially early in the season, when immunization helps most.
• Double protection: complex rules and the need to coordinate maternal and infant care may explain the 14.2% who got both.
• Recommendations matter: about half of women reported no provider recommendation — missed chances to protect infants. CDC and the American College of Obstetricians and Gynecologists offer resources to help providers talk about immunization.

Limitations

A nonprobability internet sample that may not represent all pregnant women; self-reported immunization (maternal coverage ran higher than in Vaccine Safety Datalink health records, though nirsevimab coverage matched the National Immunization Survey); small numbers for some racial and ethnic groups; and a sample missing some infants eligible for nirsevimab.

Sources

Based on "Maternal Respiratory Syncytial Virus Vaccination and Receipt of Respiratory Syncytial Virus Antibody (Nirsevimab) by Infants Aged <8 Months — United States, April 2024," by Hilda Razzaghi, Emma Garacci, Katherine E. Kahn, Megan C. Lindley, Jefferson M. Jones, Shannon Stokley, Kayla Calhoun and Carla L. Black, Morbidity and Mortality Weekly Report, Centers for Disease Control and Prevention, citing the Advisory Committee on Immunization Practices and others; a work of the United States government in the public domain. The imported title had lost the "<" in "Aged <8 Months." A social-media graphic is left out.