Duration of Protection of Nirsevimab Against Hospitalisation for Respiratory Syncytial Virus Infection

Queensland Infant Birth Dose RSV Immunisation Program 2024 - Duration of Protection and Impact

Respiratory syncytial virus (RSV) is a leading cause of hospitalizations for acute lower respiratory tract infection (LRTI) in infants. In Australia approximately 1.5% of infants are hospitalized due to RSV, 80% of whom are born full-term and are otherwise healthy. Two randomized trials have used a seasonal implementation strategy to show nirsevimab, a long-acting monoclonal antibody, has sustained efficacy against RSV LRTI hospitalizations in the first 150-180 days after administration. Nirsevimab has been approved in many countries for the prevention of RSV-LRTI in neonates and infants. However, the protection offered by nirsevimab beyond 180 days remains unknown. Queensland is a large Australian state spanning the tropical and sub-tropical climate zones, where RSV circulates year-round. The Queensland government publicly funded nirsevimab for all infants at birth from 15 April 2024. The aim of this study is to estimate the duration of effectiveness of nirsevimab against RSV-related hospitalizations.

A case-control study will be conducted using routinely collected linked data. Cases will be children born in Queensland from 15 April 2024 to 14 April 2025 who are hospitalised with an RSV-related condition prior to 14 April 2026. Controls will be drawn from the set of infants who are admitted to the same hospital in a 5:1 ratio, and matched on age and sex using the Queensland Perinatal Data Collection. Nirsevimab receipt will be extracted from hospital's electronic medical records and linked to hospitalization data by the Queensland Health Data Linkage Unit. Duration of protection against RSV-related hospitalisation due to nirsevimab will be assessed using multivariable logistic regression model accounting for matching and adjusting for confounding variables.

This case-control study will determine the level and duration of protection offered by nirsevimab in a region with year-round RSV circulation and inform future prevention strategies. Interim analysis is expected to be available at the time of the conference, allowing for early dissemination of this first evidence about nirsevimab duration of protection beyond 180 days.

Funding: From Sanofi and AstraZeneca through a collaboration grant.

Study Overview

• Status: Active, not recruiting
• Conditions: Respiratory Syncytial Viral (RSV) Infections

• Study Type: Observational
• Enrollment (Estimated): 4350

Contacts and Locations

Study Locations

• Australia
  • Queensland
    • Gold Coast, Queensland, Australia, 4215
      • Griffith University

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

Our study population will consist of all infants born in Queensland between 15 April 2024 and 30 April 2025 and hospitaliszed for any reason between 15 April 2024 and 30 April 2026.

Cases will be All infants born in Queensland between 15 April 2024 and 30 April 2025 who were admitted to any hospital in Queensland (public and private) between 15 April 2024 and 30 April 2026 with a respiratory related principle or other diagnosis (ICD codes J21.0, J20.5, J12.1, B97.4). Controls will be defined as infants admitted to the same hospital that do not have a diagnosis of (ICD codes J21.0, J20.5, J12.1, B97.4) and that the admission is not an elective admission.

For each included case, five controls (where possible) matched on month of birth and sex will be requested to enable appropriate comparison.

Description

Inclusion Criteria: Any infant born between 15 April 2024 and 30 April 2025 and hospitalized for any reason between 15 April 2024 and 30 April 2026.

Exclusion Criteria: Infants who admitted to hospitals with an elective admission. ((i.e. admissions that are planned ahead of time, such as scheduled surgeries or other pre-arranged medical procedures).

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort
RSV hospitalised infant; Description: Cases (RSV hospitalised infant) will be children born in Queensland from 15 April 2024 to 14 April 2025 who are hospitalised with a RSV-related condition prior to 14 April 2026. Nirsevimab receipt will be extracted from hospital's electronic medical records and linked to hospitalisation data by the Queensland Health Data Linkage Unit.
Non-RSV hospitalised infant; Description: Controls (Non-RSV hospitalised infant) will be drawn from the set of infants who are admitted to the same hospital in a 5:1 ratio, and matched on age and sex using the Queensland Perinatal Data Collection. Nirsevimab receipt will be extracted from hospital's electronic medical records and linked to hospitalization data by the Queensland Health Data Linkage Unit.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
The duration of effectiveness of nirsevimab against RSV-related hospitalizations.	From mid April 2024 to mid April 2026

Secondary Outcome Measures

Outcome Measure	Time Frame
Estimate the quantities of the laboratory confirmed RSV hospitalization length of stay and paediatric intensive care unit admission that were prevented by a 12-month year-round nirsevimab immunization program in Queensland infants.	From mid April 2024 to mid April 2026
Estimate the quantities of all cause acute respiratory hospitalization and PICU admissions that were prevented by nirsevimab immunization program in Queensland infants	From mid April 2024 to mid April 2026
Estimate the quantities of all death from RSV-related illness that were prevented by a 12-month year-round nirsevimab immunization program in Queensland infants	From mid April 2024 to mid April 2026
Evaluate the impact of nirsevimab on the cost of hospital services in Queensland, Australia	From mid April 2024 to mid April 2026

Collaborators and Investigators

• Sponsor: Griffith University

Study record dates

Study Major Dates

• Study Start (Actual): April 15, 2024
• Primary Completion (Estimated): April 15, 2026
• Study Completion (Estimated): March 31, 2027

Study Registration Dates

• First Submitted: May 19, 2025
• First Submitted That Met QC Criteria: May 19, 2025
• First Posted (Actual): May 29, 2025

Study Record Updates

• Last Update Posted (Actual): May 29, 2025
• Last Update Submitted That Met QC Criteria: May 19, 2025
• Last Verified: February 1, 2025

More Information

Terms related to this study

• Keywords: monoclonal antibody; Respiratory syncytial virus; Case control; nirsevimab
• Additional Relevant MeSH Terms: Infections
• Other Study ID Numbers: 2024/851; VAS00012 (Other Grant/Funding Number: Sanofi Pasteur S.A)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No