The primary objective of this study is to determine the nirsevimab immunisation rate in eligible infants (according to Queensland Paediatric Respiratory Syncytial Virus Prevention Program recommendation) in Queensland, Australia.

The study will focus on:

1. Assessing the immunisation rates among eligible infants (born from 1 February 2024 to 15 April 2025) in their first Respiratory Syncytial Virus (RSV)-season in Queensland.

Secondary objectives of this study are as follows:

1. To analyse reasons of parents to decide for or against immunisation of their infant with nirsevimab.

   1. This objective aims to assess potential influencing factors and evaluate the changes in acceptance across the three cohorts prior and post recommendation.
   2. In this regard, demographic factors (e.g. education, income) will be included in the analysis where applicable to gain insights on their potential impact.

2. To assess immunisation rates for further subgroups, e.g. by: a) risk group (defined chronic condition or pre-term birth status), b) regional areas of Queensland.

3. To compare the vaccination coverage rate estimates with data captured via the Australian Immunisation Register.

Inclusion Criteria:

• Be a parent of an infant born between 1 February 2024 and 15 April 2025
• Be at least 18 years of age
• Reside in Queensland, Australia
• Read and agree to the Participant Information and Consent Form (PICF) before proceeding to the survey
• Agree with Adverse Event (AE) reporting requirements before proceeding to the survey

Exclusion Criteria:

- Have participated in any studies on infant respiratory diseases in the past 4 months

The above information is not intended to contain all considerations relevant to a potential participation in a clinical trial.

The study will target a sample of 1,200 parents of infants born between February 2024 and April 2025.

Eligible participants must be at least 18, reside in Queensland, and not have been involved in similar research recently.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org