The primary objective of this study is to determine the nirsevimab immunization rate in eligible infants in their first RSV-season in Czechia.

The study will focus on:

1. Assessing nirsevimab immunization rates among eligible infants (according to ČVS recommendation) in their first RSV-season in Czechia (i.e. across all geographies)
2. Assessing nirsevimab immunisation rates among the "catch-up cohort", i.e. all infants born between April and September.
3. Assessing nirsevimab immunization rate among the "in-season cohort", i.e. all infants born during the RSV season between October and March.

Secondary objectives are:

1. To analyze reasons of parents to decide for or against immunization of their infant with nirsevimab.
2. To assess immunization rates for further subgroups, if sufficient sample for subgroup achieved, e.g. by: risk group (defined chronic condition or pre-term birth status)
3. To assess concordance of a parent survey results based on randomly sampled parent population using Computer-Assisted Self-Interviewing (CASI) for estimating immunization rates in Czechia with coverage calculated based on pharmacy sales data.

Inclusion Criteria:

• Be a parent of an infant born between April 2025/26 and March 2026/27, respectively
• Permanent residence in Czechia at the time of survey completion and speak Czech
• Be at least 18 years old at the time of survey completion
• Agree with privacy policy and AE (Adverse Event) reporting requirements before proceeding with the survey
• Read and agree to the ICF (Informed Consent Form) by ticking a box before proceeding with the survey

Exclusion criteria:

• N/A

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 250 parents of infants born between April 2025 and March 2027.

Eligible participants must be at least 18, reside in Czechia at the time of survey completion and speak Czech.

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