P1.182: Impact of Maternal RSV Vaccination (Abrysvo) and Monoclonal Antibody (Beyfortus) on Reducing the Severity of RSV-related Illness in a Multiethnic Immigrant Population

Background: Respiratory Syncytial Virus (RSV) is a leading cause of lower respiratory tract infections in infants, often resulting in hospitalizations and the necessity for respiratory support, particularly during peak season for those under 6 months of age. In 2023, the U.S. FDA approved two preventive strategies to reduce the burden of RSV disease in this vulnerable population: Pfizer’s RSV vaccine (Abrysvo) for pregnant women between 32 and 36 weeks of gestation (August 2023) and Nirsevimab, a long-acting monoclonal antibody for infants (July 2023). Real-world data regarding the impact of these preventive strategies on RSV-related disease severity is now becoming available. We share our experience utilizing comparative analysis of hospitalizations, respiratory support needs, and outcomes with 180 days of follow-up.

Methods: Our IRB-approved study examined a cohort of 1,259 infants born between October 2023 and March 2024 by reviewing their Electronic Medical Records (EPIC system) at a large public hospital that serves a diverse, multiethnic patient population at NYC H+H/Elmhurst Hospital in Queens, NY. The study included all infants who received Nirsevimab before discharge and/or whose mothers received Abrysvo antenatally between 32 and 34 weeks of gestation, with follow-up until 180 days post-administration. We recorded infant demographics, baseline clinical characteristics, and any adverse reactions to Abrysvo or Nirsevimab. Effectiveness was assessed by reviewing RSV-associated illnesses requiring healthcare utilization within this cohort.

Results: In this study cohort, 37 (2.9%) infants tested positive for RSV. Among them, 15 were in the prevention group, which received either Beyfortus or Abrysvo. Within this group, 1 infant (6.67%) required hospitalization due to RSV infection. In contrast, the no prevention group, consisting of 22 infants who did not receive any RSV prevention, had 9 infants (40.91%) who required hospitalization. The chi-square test revealed a statistically significant difference (p-value of 0.0213) between these groups, suggesting that the RSV prevention group had fewer hospitalizations compared to the no prevention group. In the no prevention group, 6 out of 22 infants (27.27%) required oxygen support via a high-flow nasal cannula, whereas the prevention group had no infants needing oxygen support (p = 0.0271). Additionally, the effect size (Phi Coefficient = -0.3633) indicates a moderate negative association between RSV prevention and the requirement for oxygen support.

Conclusion: This study showed that the infants receiving either Beyfortus or Abrysvo in our highly diverse population had significantly fewer hospitalizations, oxygen support needs, and high-flow cannula requirements compared to those who did not receive any RSV prevention. Our findings affirm the reduction of severe complications in RSV-positive infants when they received RSV prevention measures via Abrysvo or Beyfortus.