A Phase 3 interventional study of RSVpreF and Placebo in Respiratory Syncytial Virus (RSV), sponsored by Pfizer. Recruiting at 20 sites in 4 countries. Open to participants aged 5 Years to 17 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-11-06.
Sponsored by Pfizer · Phase 3, Interventional, and Prevention
The purpose of the study is to evaluate the safety, tolerability, and immunogenicity of RSVpreF in children 5 to \<18 years of age at high risk for RSV disease, including those who are immunocompromised.
The study will first enroll immunocompetent, RSV-experienced participants before enrolling immunocompromised participants to allow for safety data review. Both Cohorts 1 (chronic conditions) and 2 (immunocompromising conditions) will be stratified into 2 age strata. Cohort 1a will enroll participants 12 to \<18 years of age with chronic medical conditions and Cohort 1b will enroll participants 5 to \<12 years of age with chronic medical conditions. Cohort 2a will enroll immunocompromised participants 12 to \<18 years of age and Cohort 2b will enroll immunocompromised participants 5 to \<12 years of age.
Pfizer is the lead sponsor of 3,334 studies on the registry; 149 are open to participants now.
Of its 601 completed or terminated interventional studies of FDA-regulated products, 391 (65%) have results posted.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria:
Chronic medical conditions:
Immunocompromising conditions:
Cohort 1a: ≥30.0 kg at enrollment Cohort 1b: ≥14.5 kg at enrollment Cohort 2a : ≥30 kg at enrollment Cohort 2b: ≥14.5 kg at enrollment
•The participant's parent(s)/legal guardian is capable of giving signed , which includes compliance with the requirements and restrictions listed in the ICD and in the protocol. Depending on the age of the participant and according to local requirements, participants will also be asked to provide assent as appropriate (verbal or written)
Key Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
The number of CD4 cells, a type of white blood cell, in a given amount of blood. It is used to follow how well the immune system is doing in HIV.
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
CD4 count
The number of CD4 cells, a type of white blood cell, in a given amount of blood. It is used to follow how well the immune system is doing in HIV.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Immunosuppression
A weakened immune system. It can come from an illness, such as HIV or some blood cancers, or from medicines that turn the immune system down, for example after an organ transplant or for an autoimmune disease; steroids at higher doses count.
Read whether the line is about a condition or about medicines, and which medicines and doses it means.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cohort 1 (a and b): Participants will receive a single dose of RSVpreF at the first study visit.
Biological: RSVpreF
Cohort 1 (a and b): Participants will receive a single dose of placebo at the first study visit.
Biological: Placebo
Cohort 2 (a and b): Participants will receive 1 dose of RSVpreF at the first study visit, and 1 dose of RSVpreF at the 12-month visit.
Biological: RSVpreF
Cohort 2 (a and b): Participants will receive 1 dose of RSVpreF at the first study visit, and 1 dose of placebo at the 12-month visit.
Biological: RSVpreF · Biological: Placebo
RSVpreF Vaccine
Placebo
Cohort 1: Proportion of participants reporting pre-specified local reactions within 7 days following investigational product administration
Describe pre-specified local reactions in children 5 to \<18 years of age with chronic medical conditions
Time frame: Within 7 days
Cohort 2: Proportion of participants reporting pre-specified local reactions within 7 days following each investigational product administration
Describe pre-specified local reactions in children 5 to \<18 years of age with immunocompromising conditions
Time frame: Within 7 days
Cohort 1: Proportion of participants reporting pre-specified systemic events within 7 days following investigational product administration
Describe pre-specified systemic events in children 5 to \<18 years of age with chronic medical conditions
Time frame: Within 7 days
Cohort 2: Proportion of participants reporting pre-specified systemic events within 7 days following each investigational product administration
Describe pre-specified systemic events in children 5 to \<18 years of age with immunocompromising conditions
Time frame: Within 7 days
Cohort 1: Proportion of participants reporting adverse events (AEs) through 1 month following investigational product administration
Describe AEs in children 5 to \<18 years of age with chronic medical conditions
Time frame: From vaccination through 1 month after vaccination
Cohort 2: Proportion of participants reporting adverse events (AEs) through 1 month following last investigational product administration
Describe AEs in children 5 to \<18 years of age with immunocompromising conditions
Time frame: From vaccination through 1 month after last vaccination
Cohort 1: Proportion of participants reporting serious adverse events (SAEs) throughout the study
Describe SAEs in children 5 to \<18 years of age with chronic medical conditions
Time frame: From vaccination through 24 months after vaccination
Cohort 2: Proportion of participants reporting serious adverse events (SAEs) throughout the study
Describe SAEs in children 5 to \<18 years of age with immunocompromising conditions
Time frame: From vaccination through 12 months after last vaccination
Cohort 1: Proportion of participants reporting newly diagnosed chronic medical conditions (NDCMCs) throughout the study
Describe NDCMCs in children 5 to \<18 years of age with chronic medical conditions
Time frame: From vaccination through 24 months after vaccination
Cohort 2: Proportion of participants reporting newly diagnosed chronic medical conditions (NDCMCs) throughout the study
Describe NDCMCs in children 5 to \<18 years of age with immunocompromising conditions
Time frame: From vaccination through 12 months after last vaccination
Cohort 1: Geometric mean ratio (GMR), estimated by the ratio of the geometric mean titers (GMTs) for RSV A and RSV B serum neutralizing titers (NTs) 1 month after vaccination in participants in Study C3671017 Cohort 1 compared to those in Study C3671013
Demonstrate that the immune responses elicited by RSVpreF in children 5 to \<18 years of age with chronic medical conditions are noninferior to the immune responses in adults ≥60 years of age
Time frame: 1 month after vaccination
Cohort 1: Seroresponse rate of RSV A and RSV B serum NTs at 1 month after vaccination
Demonstrate that the immune responses elicited by RSVpreF in children 5 to \<18 years of age with chronic medical conditions are noninferior to the immune responses in adults ≥60 years of age. Seroresponse is defined as a postvaccination NT ≥4 times the lower limit of quantitation (LLOQ) if the prevaccination titer is below the LLOQ; or a ≥4-fold rise from prevaccination if the prevaccination titer is ≥ LLOQ
Time frame: 1 month after vaccination
Cohort 2: Neutralizing Titers (NTs) for RSV A and RSV B expressed as Geometric Mean Titers (GMT)
Describe the immune responses elicited by 1 or 2 doses of RSVpreF in children 5 to \<18 years of age with immunocompromising conditions
Time frame: Before each vaccination, 1 month after each vaccination, 12 months after last vaccination
Cohort 2: NTs for RSV A and RSV B expressed as Geometric Mean Fold Rise (GMFR)
Describe the immune responses elicited by 1 or 2 doses of RSVpreF in children 5 to \<18 years of age with immunocompromising conditions
Time frame: 1 month after each vaccination, 12 months after last vaccination
Cohort 2: NTs for RSV A and RSV B expressed as seroresponse rate
Describe the immune responses elicited by 1 or 2 doses of RSVpreF in children 5 to \<18 years of age with immunocompromising conditions
Time frame: 1 month after each vaccination, 12 months after last vaccination
Cohort 1: NTs for RSV A and RSV B expressed as Geometric Mean Titers (GMT)
Describe the immune responses elicited by RSVpreF in children 5 to \<18 years of age with chronic medical conditions
Time frame: Before vaccination, 1 month after vaccination, 12 months after vaccination, 24 months after vaccination
Cohort 1: NTs for RSV A and RSV B expressed as GMFR
Describe the immune responses elicited by RSVpreF in children 5 to \<18 years of age with chronic medical conditions
Time frame: 1 month after vaccination, 12 months after vaccination, 24 months after vaccination
Cohort 1: NTs for RSV A and RSV B expressed as seroresponse rate
Describe the immune responses elicited by RSVpreF in children 5 to \<18 years of age with chronic medical conditions. Seroresponse is defined as a postvaccination NT ≥4 times the lower limit of quantitation (LLOQ) if the prevaccination titer is below the LLOQ; or a ≥4-fold rise from prevaccination if the prevaccination titer is ≥ LLOQ
Time frame: 1 month after vaccination, 12 months after vaccination, 24 months after vaccination
Plan to share: Yes — 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.
Data sharing details ↗ · www.pfizer.com
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: Abrysvo