Retrospective study validates nirsevimab role against RSV in infants

A retrospective cohort study evaluating participants from Catalonia, Spain reinforces the potential of immunoprophylaxis with the novel monoclonal antibody nirsevimab in combating respiratory syncytial virus (RSV)-related outcomes in infants in the hospital and primary care settings.

“RSV is a major cause of bronchiolitis and hospitalization in children under 5 years … Our study reveals substantial effectiveness, with an 87.6-percent reduction in hospital admissions and a 90.1-percent reduction in admissions to the paediatric intensive care unit (PICU) due to RSV bronchiolitis,” said Dr Antoni Soriano-Arandes from the Paediatric Infectious Diseases and Immunodeficiencies Unit, Children’s Hospital, Vall d’Hebron Barcelona Hospital Campus, Barcelona, Spain, during his presentation at ESPID 2024.

The adjusted hazard ratios (HRs) for RSV-associated hospital admission and PICU admission were 0.124 (95 percent confidence interval [CI], 0.086–0.179) and 0.099 (95 percent CI, 0.041–0.237), respectively. [ESPID 2024, abstract O052]

When looking at the Kaplan-Meier curves, Soriano-Arandes noted that the differences between the nirsevimab and control arms for both outcomes were ‘impressive’.

There were also notable reductions in less severe outcomes, which include RSV infections verified via rapid antigen test (68.9 percent), viral pneumonia diagnosed in primary care (60.7 percent), hospital emergency department visits due to bronchiolitis (55.4 percent), and primary care-attended bronchiolitis (48.1 percent).

The adjusted HRs for these outcomes were 0.311 (95 percent CI, 0.200–0.483), 0.393 (95 percent CI, 0.203–0.758), 0.446 (95 percent CI, 0.385–0.516), and 0.519 (95 percent CI, 0.467–0.576), respectively.

Findings inform RSV prevention strategies

In October 2023, nirsevimab was introduced in the infant immunization programme in the northeast region of Spain. To evaluate its effectiveness in infants born between April and September 2023 during their first epidemic season, Soriano-Arandes and colleagues did a retrospective cohort analysis using data gathered from five Catalan health databases.

A total of 23,127 infants (median age 88 days) comprised the nirsevimab group, while 3,398 were included in the control group (median age 106 days). Half of the overall cohort were boys. Over three-quarters (76.3 percent) of participants in the nirsevimab arm received the drug within the first month of the immunization campaign.

When comparing the epidemiological data for Catalonian hospitals between 2022–2023 and 2023–2024, a substantial drop was seen during the latter period in terms of hospitalizations and emergency attendances among children under 1 year of age. [https://sivic.salut.gencat.cat/vrs, accessed June 24, 2024]

“These findings offer timely and crucial insights for healthcare authorities, informing strategies for RSV prevention and planning of immunization campaigns,” Soriano-Arandes concluded.