A Study to Learn Safety and Immune Response to Study Vaccine -RSVpreF in Adults at High Risk of Severe RSV Disease.

A PHASE 3, MULTICENTER, SINGLE-ARM, OPEN-LABEL STUDY TO EVALUATE THE SAFETY, TOLERABILITY, AND IMMUNOGENICITY OF RESPIRATORY SYNCYTIAL VIRUS (RSV) PREFUSION F SUBUNIT VACCINE IN ADULTS CONSIDERED AT HIGH RISK OF SEVERE RSV DISEASE IN JAPAN

The purpose of the study is to learn about the immune response after a RSVpreF vaccination. This study is being conducted in Japan. RSV is a common virus that can cause infections of the lungs and airways.

The study is seeking participants who are:

• 18 to 59 years of age
• adults with health condition(s) that can put them at an increased risk of severe RSV disease

It will also learn about the safety of RSVpreF vaccination. The study lasts about 2 months. Adults need to visit the research site at least 2 times. The participant will receive a phone call 2 months after vaccination for health checks.

Study Overview

• Status: Recruiting
• Conditions: Respiratory Syncytial Virus (RSV)
• Intervention / Treatment: Biological: RSVpreF

Detailed Description

This is a Phase 3, multicenter, single-arm, open-label study that will assess the safety, tolerability, and immunogenicity of Pfizer's RSVpreF in adults 18 to 59 years of age considered to be at high risk of RSV disease due to certain chronic medical conditions in Japan.

Approximately 130 participants 18 to 59 years of age considered at high risk of RSV disease due to certain chronic medical conditions will be enrolled to receive RSVpreF.

The total duration of trial participation for each participant will be 2 months.

After screening and confirmation of eligibility, a prevaccination blood sample will be collected for immunogenicity assessments and a single dose of study intervention (RSVpreF) will be administered.

Participants will report daily reactogenicity data using an electronic device for 7-days or until resolution.

Participants will return approximately 1 month later for a follow-up blood draw for immunogenicity assessments and collection of safety information.

A telephone follow-up visit will be conducted approximately 2 months after vaccination to collect safety information.

• Study Type: Interventional
• Enrollment (Estimated): 130
• Phase: Phase 3

Contacts and Locations

• Study Contact: Name: Pfizer CT.gov Call Center; Phone Number: 1-800-718-1021; Email: ClinicalTrials.gov_Inquiries@pfizer.com

Study Locations

• Japan
  • Fukuoka, Japan, 810-0021
    • Recruiting
    • Tenjin Sogo Clinic
  • Ibaraki
    • Tsuchiura, Ibaraki, Japan, 300-0062
      • Recruiting
      • Tsuchiura Beryl Clinic
  • Tokyo
    • Chuo-ku, Tokyo, Japan, 104-0031
      • Recruiting
      • Fukuwa Clinic
    • Chuo-ku, Tokyo, Japan, 103-0027
      • Recruiting
      • Tokyo-Eki Center-building Clinic
    • Chuo-ku, Tokyo, Japan, 103-0025
      • Recruiting
      • Nihonbashi Sakura Clinic

Participation Criteria

Eligibility Criteria

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

Description

Key Inclusion Criteria:

• Underlying health condition(s) that can put the participant at an increased risk of severe RSV/complications including chronic lung , heart, kidney, liver, nervous system, blood, or metabolic diseases

Key Exclusion Criteria:

• Received any kind of RSV vaccine before participating in this study
• Determined as not eligible by the investigator based on the participant's past and present health condition(s), medication(s) and treatment(s)

Please refer to the study contact for further eligibility details.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Prevention
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: RSVpreF; RSV Vaccine	Biological: RSVpreF; RSV Vaccine

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Percentage of participants reporting prompted systemic events within 7 days following investigational product administration	Describe prompted systemic events following investigational product administration	Day 7
Percentage of participants reporting prompted local reactions within 7 days following investigational product administration	Describe prompted local reactions following investigational product administration	Day 7
Percentage of participants reporting adverse events (AEs) through 1 month following investigational product administration	Describe AEs occurring through 1 month following administration of investigational product	1 month after vaccination
Percentage of participants reporting serious adverse events (SAEs) throughout the study	Describe SAEs through 2 months following administration of investigational product	2 months after vaccination
Geometric Mean Titer (GMT) ratio (GMR) , estimated by the ratio of the GMTs for RSV subgroup A (RSV A) and RSV subgroup B (RSV B) neutralizing titers (NTs) with RSVpreF in this study's participants to that in Study C3671013 Japanese older adults	Demonstrate that the immune responses to RSVpreF in this study participant are similar to those in Study C3671013 Japanese older adults	1 month after vaccination

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
GMT of NTs for RSV A and RSV B	Describe the immune responses to RSVpreF with GMT of NTs for RSV A and RSV B before vaccination and at 1 month after vaccination.	1 month after vaccination
Geometric mean fold rise (GMFR) of NTs for RSV A and RSV B	Describe the immune responses to RSVpreF with GMFR of NTs for RSV A and RSV B from before vaccination to 1 month after vaccination.	1 month after vaccination
Seroresponse rate of NTs for RSV A and RSV B	Describe the immune responses to RSVpreF with seroresponse rate of NTs for RSV A and RSV B at 1 month after vaccination. Seroresponse is defined as a postvaccination NT ≥4 times the lower limit of quantitation (LLOQ) if the baseline titer is below the LLOQ; or a ≥	1 month after vaccination

Collaborators and Investigators

• Sponsor: Pfizer
• Investigators: Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

Helpful Links

• To obtain contact information for a study center near you, click here.

Study record dates

Study Major Dates

• Study Start (Actual): May 11, 2026
• Primary Completion (Estimated): August 31, 2026
• Study Completion (Estimated): August 31, 2026

Study Registration Dates

• First Submitted: April 15, 2026
• First Submitted That Met QC Criteria: April 15, 2026
• First Posted (Actual): April 21, 2026

Study Record Updates

• Last Update Posted (Actual): June 2, 2026
• Last Update Submitted That Met QC Criteria: May 28, 2026
• Last Verified: May 1, 2026

More Information

Terms related to this study

• Keywords: RESPIRATORY SYNCYTIAL VIRUS (RSV); ADULTS AT HIGH RISK
• Other Study ID Numbers: C3671060

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.

Drug and device information, study documents

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