Respiratory Syncytial Virus Vaccine and Nirsevimab Uptake Among Pregnant People and Their Neonates

Abstract

Importance: Two interventions to prevent severe respiratory syncytial virus (RSV) in infants were approved in 2023-a bivalent prenatal RSV prefusion F protein-based (RSVpreF) vaccine and an infant monoclonal antibody (nirsevimab). Understanding their uptake and clinical outcomes is essential for public health planning.

Objective: To describe uptake of the prenatal RSVpreF vaccine and infant nirsevimab.

Design, setting, and participants: This retrospective cohort study was conducted at a single academic center among 647 pregnant individuals eligible for RSVpreF vaccination (32-36 weeks' gestation between October 15, 2023, and January 31, 2024) and infants eligible for nirsevimab (no prenatal RSVpreF vaccination >14 days before delivery).

Exposure: Pregnancy or birth during the 2023-2024 RSV season.

Main outcomes and measures: RSVpreF vaccination among eligible pregnant individuals and nirsevimab administration prior to hospital discharge among eligible infants.

Results: Of 647 eligible pregnant individuals (mean [SD] age, 34.6 [6.2] years; 355 nulliparous [54.9%]; 558 privately insured [86.2%]), 414 (64.0%) received the RSVpreF vaccine. Factors associated with higher RSVpreF uptake included older birthing parent age (adjusted odds ratio [AOR], 1.09; 95% CI, 1.05-1.12), nulliparity (AOR, 1.84; 95% CI, 1.31-2.60), private insurance (AOR, 2.19; 95% CI, 1.27-3.80), non-Hispanic ethnicity (AOR, 2.36; 95% CI 1.57-3.55; reference: Hispanic), receipt of any COVID-19 vaccine (AOR, 7.12; 95% CI, 3.91-13.70), 2023-2024 formula COVID-19 booster vaccine (AOR, 5.62; 95% CI, 3.80-8.48), influenza vaccine (AOR, 8.14; 95% CI, 5.38-12.50), or tetanus-diphtheria-pertussis vaccine (AOR, 6.86; 95% CI, 3.79-13.10). Factors associated with lower RSVpreF uptake included non-English language preference (AOR, 0.24; 95% CI, 0.10-0.52), Black race (AOR, 0.30; 95% CI, 0.16-0.57; reference: Asian), other or unknown race (AOR, 0.48; 95% CI, 0.30-0.76), and multiple gestation (AOR, 0.27; 95% CI, 0.07-0.88). Nirsevimab was administered to 183 of 261 eligible infants (70.1%) prior to hospital discharge. Among those who did not receive RSVpreF or standard prenatal vaccines, 40.4% of their neonates (19 of 47) received nirsevimab; among those who declined infant hepatitis B vaccination, 34.0% of their neonates (17 of 50) received nirsevimab. Respiratory syncytial virus coverage exceeded 80% during all months of the study period except October 2023, the first month during which prenatal RSV vaccination and infant nirsevimab were available. Preterm delivery occurred in 35 of 414 RSVpreF-vaccinated individuals (8.5%) and 43 of 233 unvaccinated individuals (18.5%). In a nested case-control analysis with preterm birth as the outcome, there was no significant association between RSVpreF vaccination and preterm birth (AOR, 1.03; 95% CI, 0.55-1.93).

Conclusions and relevance: In this cohort study, uptake of the RSVpreF vaccine and infant nirsevimab was high. Nirsevimab uptake was high even among individuals who did not receive routine prenatal or infant vaccines. There was no significant association between RSVpreF vaccination and preterm birth. This study suggests that an RSV prevention strategy that included both prenatal vaccination and infant monoclonal antibody administration had high uptake and reassuring perinatal outcomes.

Figure 1.. Uptake of Prenatal Vaccines and Infant Nirsevimab

A, Monthly proportion of newborns during the study period who were protected against respiratory syncytial virus (RSV), either through bivalent RSV prefusion F protein (RSVpreF) vaccination administered at least 14 days before delivery or infant nirsevimab administration prior to hospital discharge. B, Uptake of vaccines during pregnancy. Tdap indicates tetanus-diphtheria-pertussis.

Figure 2.. Univariable and Multivariable Logistic Regression Analyses for Characteristics Associated With Bivalent Respiratory Syncytial Virus Prefusion F Protein (RSVpreF) Vaccination Among Eligible Pregnant Individuals

For adjusted estimates, a directed acyclic graph (eFigure 2 in Supplement 1) was used to represent our assumptions of the causal structure and to guide covariate selection for adjustment, ensuring that only those necessary to close backdoor paths between the risk factor of interest and the outcome were included. Race and ethnicity data were obtained from the electronic medical record. The “other” race category included self-reported other race, Native American or Alaska Native, and Native Hawaiian or Pacific Islander. Early fetal growth restriction includes cases diagnosed prior to 32 weeks’ gestation. The odds ratio (OR) for age represents the change in odds of RSVpreF vaccination associated with each 1-year increase in age. Tdap indicates tetanus-diphtheria-pertussis.

Figure 3.. Univariable and Multivariable Logistic Regression Analyses for Characteristics Associated With Neonatal Nirsevimab Administration Prior to Hospital Discharge

For adjusted estimates, a directed acyclic graph (eFigure 3 in Supplement 1) was used to represent our assumptions of the causal structure and to guide covariate selection for adjustment, ensuring that only those necessary to close backdoor paths between the risk factor of interest and the outcome were included. Race and ethnicity data were obtained from the electronic medical record. The “other” race category included self-reported other race, Native American or Alaska Native, and Native Hawaiian or Pacific Islander. Early fetal growth restriction includes cases diagnosed prior to 32 weeks’ gestation. The odds ratio (OR) for age represents the change in odds of nirsevimab administration associated with each 1-year increase in birthing parent age. Tdap indicates tetanus-diphtheria-pertussis.