Strategies used to improve immunization coverage of nirsevimab in an autonomous community in Spain

Abstract

Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections, particularly in infants under one year. In 2023, Spain became one of the first countries to implement nirsevimab, a long-acting monoclonal antibody, for RSV prevention. This study evaluates the second immunization campaign in the Region of Murcia, focusing on coverage, timeliness, and equity. A retrospective cross-sectional analysis included children born between April 2024 and March 2025. Coverage was assessed for infants born during and outside the RSV season. Continuous training for healthcare professionals and targeted family education were implemented to improve uptake. Of 12,606 children, 11,785 (93.5%) received nirsevimab, with coverage higher for those born during the campaign (96.0%) than before (90.5%, p < .001). Coverage was higher among children whose health card holder was born in Spain (94.2%) versus abroad (91.9%, p < .001), reducing the previous season's gap from 5.7% to 2.3%. Most infants (92.4%) were immunized before maternity discharge, with delayed cases receiving protection at a mean age of 22.7 d. High protocol adherence (99.7%) and rapid catch-up immunization were observed. Continuous professional training and public information contributed to improved coverage, timely protection, and reduced inequities, demonstrating the feasibility of nirsevimab implementation in a public health program.