Publication Date
3-7-2024
Journal
Morbidity and Mortality Weekly Report
DOI
10.15585/mmwr.mm7309a4
PMID
38457312
PMCID
PMC10932582
PubMedCentral® Posted Date
3-7-2024
PubMedCentral® Full Text Version
Post-print
Published Open-Access
yes
Keywords
Infant, Child, Humans, United States, Respiratory Syncytial Virus Vaccines, Seasons, Respiratory Syncytial Virus, Human, Respiratory Syncytial Virus Infections, Hospitalization, Respiratory Tract Infections, Antibodies, Monoclonal, Humanized
Abstract
Respiratory syncytial virus (RSV) is the leading cause of hospitalization among infants in the United States. In August 2023, CDC's Advisory Committee on Immunization Practices recommended nirsevimab, a long-acting monoclonal antibody, for infants agedtrials, nirsevimab efficacy against RSV-associated lower respiratory tract infection with hospitalization was 81% (95% CI = 62%-90%) through 150 days after receipt; post-introduction effectiveness has not been assessed in the United States. In this analysis, the New Vaccine Surveillance Network evaluated nirsevimab effectiveness against RSV-associated hospitalization among infants in their first RSV season during October 1, 2023-February 29, 2024. Among 699 infants hospitalized with acute respiratory illness, 59 (8%) received nirsevimab ≥7 days before symptom onset. Nirsevimab effectiveness was 90% (95% CI = 75%-96%) against RSV-associated hospitalization with a median time from receipt to symptom onset of 45 days (IQR = 19-76 days). The number of infants who received nirsevimab was too low to stratify by duration from receipt; however, nirsevimab effectiveness is expected to decrease with increasing time after receipt because of antibody decay. Although nirsevimab uptake and the interval from receipt of nirsevimab were limited in this analysis, this early estimate supports the current nirsevimab recommendation for the prevention of severe RSV disease in infants. Infants should be protected by maternal RSV vaccination or infant receipt of nirsevimab.