595 - Nirsevimab Administration to Infants in the Neonatal Intensive Care Unit (NICU): A Single-Center Experience

Publication Number: 595.5939

Emily A. Messick, Nationwide Children's Hospital, Columbus, OH, United States; Wai-Yin mandy. Tam, Nationwide Children's Hospital, columbus, OH, United States; Jacqueline Magers, Nationwide Children's Hospital, Columbus, OH, United States; Alexandra F.. Burton, Nationwide Children's Hospital, Westerville, OH, United States; Michael A. Storey, Nationwide Children's Hospital, Columbus, OH, United States; Pablo J. Sanchez, Nationwide Children's Hospital -OSU, Columbus, OH, United States

Background: Nirsevimab is recommended for all infants discharged from the NICU during the respiratory syncytial virus (RSV) season to prevent serious RSV disease but its tolerance in high-risk infants is not well known.

Objective: To determine the frequency of adverse events following administration of nirsevimab to high-risk infants in a level III NICU.

Design/Methods: The occurrence of apnea/bradycardia/desaturation (A/B/D) episodes in some preterm infants following nirsevimab administration at the time of NICU discharge prompted an observational study from 10/25/2023 to 3/8/2024 to examine potential adverse events. Specifically, occurrence of A/B/D and oral feeding (PO) percentage were determined from 3 days before to up to 3 days after receipt of nirsevimab. Infants who experienced A/B/D or decrease in PO ≥ 20% after receipt of nirsevimab were compared to infants who tolerated nirsevimab without A/B/D or decrease in PO. Days to discharge from nirsevimab administration was evaluated, as well as RSV readmission after discharge. Data were analyzed using Kruskal Wallis test for continuous outcomes and Fisher’s exact test for categorical outcomes.

Results: During the 2023-24 RSV season, 173 of 367 infants received nirsevimab before NICU discharge. Reasons for not receiving nirsevimab included maternal RSV vaccination during pregnancy, transfer to higher level NICU, and parental hesitancy. Ten (6%) of the 173 infants (gestational ages from 24-36 weeks) had A/B/D (n=7) or decrease in PO ≥ 20% (n=3) following nirsevimab administration. Infants who had predefined adverse event(s) did not differ from those who experienced no ill effect in birth weight, gestational age, male sex, bronchopulmonary dysplasia, maximum respiratory support during NICU stay and at time of receipt of nirsevimab. The infants also did not differ in chronologic or corrected age on the day of nirsevimab administration (Table 1). Six of the 10 infants with an adverse event also received at least one vaccine ≤ 3 days before nirsevimab (n=5 received hepatitis B vaccine, n=1 received DTaP/IPV/HEP-B/HiB and pneumococcal vaccine). The occurrence of an adverse event was associated with prolonged hospitalization. None had fever or local cutaneous reactions. One infant who tolerated nirsevimab without A/B/D or decreased PO was readmitted with RSV and COVID-19 infection.

Conclusion(s): Most infants tolerated nirsevimab without ill effects. However, a temporal association between receipt of nirsevimab and A/B/D and/or poor feeding occurred in 6% of infants. Monitoring of infants in the NICU after nirsevimab administration may be advisable.

Table 1: Characteristics and Outcomes of Infants who Received Nirsevimab in the NICU during the 2023-2024 RSV Season