An Observational Study to Assess Nirsevimab Immunization Rates in Eligible Infants During Their First RSV Season in the Czechia

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.

Study Overview

• Status: Not yet recruiting
• Conditions: RSV Immunization
• Intervention / Treatment: Biological: Nirsevimab Respiratory Syncytial Virus monoclonal antibody

• Study Type: Observational
• Enrollment (Estimated): 250

Contacts and Locations

• Study Contact: Name: Trial Transparency email recommended (Toll free for US & Canada); Phone Number: option 6 800-633-1610; Email: contact-us@sanofi.com

Study Locations

• Czechia
  • Prague, Czechia, 160 00
    • Sanofi s.r.o.

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Non-Probability Sample

Study Population

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.

Description

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.

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Cohort 1; "Catch-up cohort", i.e. all infants born between April and September in Czechia.	Biological: Nirsevimab Respiratory Syncytial Virus monoclonal antibody; This study will not administer any treatment, only observe the treatment as prescribed in real-world clinical practice
Cohort 2; "In-season cohort", i.e. all infants born during the RSV season between October and March in Czechia.	Biological: Nirsevimab Respiratory Syncytial Virus monoclonal antibody; This study will not administer any treatment, only observe the treatment as prescribed in real-world clinical practice

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
The proportion of immunised infants among all enrolled infants	A descriptive analysis of immunisation status (yes/no) will be performed using summary statistics.	June 2026 - July 2026
Type of immunisation	A descriptive analysis of immunisation status (yes/no) will be performed using summary statistics.	June 2026 - July 2026
Location of immunization	A descriptive analysis of immunisation status (yes/no) will be performed using summary statistics.	June 2026 - July 2026

Collaborators and Investigators

• Sponsor: Sanofi

Study record dates

Study Major Dates

• Study Start (Estimated): June 15, 2026
• Primary Completion (Estimated): July 17, 2026
• Study Completion (Estimated): July 17, 2026

Study Registration Dates

• First Submitted: June 3, 2026
• First Submitted That Met QC Criteria: June 3, 2026
• First Posted (Actual): June 9, 2026

Study Record Updates

• Last Update Posted (Actual): June 9, 2026
• Last Update Submitted That Met QC Criteria: June 3, 2026
• Last Verified: June 1, 2026

More Information

Terms related to this study

• Keywords: nirsevimab;; nirsevimab immunization rates
• Other Study ID Numbers: RSV25849

Plan for Individual participant data (IPD)

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

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No