First year of nirsevimab use in Argentina (2025): Report from a private vaccination center.

Introduction. Since March 2025, nirsevimab, a monoclonal antibody for the prevention of respiratory syncytial virus infection (RSV), has been available in Argentina. The objective of this study was to describe the use of nirsevimab at a private vaccination center in the Buenos Aires Metropolitan Area, including the profile of infants vaccinated during its first year on the market. Population and methods. A descriptive study was conducted using an online survey administered to caregivers of children who received nirsevimab. The study analyzed sociodemographic variables, medical history, maternal RSV vaccination status, and the reason for the recommendation. Results. A total of 232 caregivers responded; 93.5% were mothers, with a mean age of 37.1 years (SD 5.4); 92.7% had a college or university education; 99.6% had health insurance. The mean age of the immunized children was 6.0 months (SD 3.9; range 0-21); 53.9% were male (N=125); 19.8% attended daycare (N = 46); 10.8% (N = 25) had comorbidities, primarily heart disease (5.6%; N = 13) and chronic respiratory disease (4.7%; N = 11); 19.0% (N = 44) had ≥1 episode of bronchiolitis. Reasons for recommendation: unvaccinated mother: 51.3% (N = 119); maternal vaccination in the previous year: 18.5% (N = 43); preterm infants <34 weeks: 14.7% (N = 34); risk factors: 6.5% (N = 15). The recommendation came from the pediatrician in 81.5% of cases (N = 189). Conclusion. More than half of the administered doses were applied to infants who lacked protection from maternal immunity. Most were healthy infants during their first season and were recommended for immunization by their pediatrician.