A Phase 2 interventional study of RSV vaccine candidate and Placebo in Respiratory Syncytial Virus Infection and Healthy Volunteers, sponsored by Sanofi Pasteur, a Sanofi Company. Completed at 25 sites in 6 countries. Open to participants aged 60 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-03-10.
Sponsored by Sanofi Pasteur, a Sanofi Company (part of Sanofi) · Phase 2, Interventional, and Prevention
The purpose of this Phase IIb study is to evaluate the efficacy of the RSV vaccine candidate for the prevention of lower respiratory tract disease (LRTD) due to RSV.
The study will enroll approximately 4500 adults aged 60 years and older in a 1:1 ratio to receive a single intra-muscular (IM) administration of either a pre-determined dose of the RSV vaccine candidate or placebo.
Study duration per participant:
6 months.
Treatment Duration:
1 IM injection. Participants will be followed for approximately 6 months post- vaccination.
306 studies on the registry are indexed under Respiratory Syncytial Virus Infections; 50 are open to participants now.
This study's enrollment of 4,541 is above the median of 89 across 223 interventional studies indexed under Respiratory Syncytial Virus Infections.
Browse Respiratory Syncytial Virus Infections studies →Sanofi Pasteur, a Sanofi Company is the lead sponsor of 374 studies on the registry; 4 are open to participants now.
Of its 94 completed or terminated interventional studies of FDA-regulated products, 73 (78%) have results posted.
First submitted after Sanofi Pasteur became part of Sanofi.
Counted across the registry records on this site, refreshed daily.
Inclusion Criteria:
A female participant is eligible to participate if she is not pregnant or breastfeeding and:
Exclusion Criteria: Participants are excluded from the study if any of the following criteria apply:
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.
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
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.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Childbearing potential
Able to become pregnant: from the first period until menopause, unless permanently unable to through surgery (removal of the womb, or of both ovaries or both fallopian tubes).
Criteria for people of childbearing potential usually ask for a negative pregnancy test and for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Postmenopausal
Periods have stopped for good: usually no period for 12 months in a row without another medical reason, sometimes confirmed by a blood test (FSH).
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.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will be enrolled in a 1:1 ratio to receive a single IM administration of the RSV vaccine candidate.
Biological: RSV vaccine candidate
Participants will be enrolled in a 1:1 ratio to receive a single IM administration of the placebo.
Biological: Placebo
Pharmaceutical form:Suspension for injection-Route of administration:Intramuscular Injection
Pharmaceutical form:Suspension for injection-Route of administration:Intramuscular Injection
Presence of the first episode of RSV-LRTD (RSV A and/or RSV B) ≥ 14 days after vaccination
Number of participants experiencing RSV-LRTD (RSV A and/or RSV B) ≥ 14 days after vaccination
Time frame: ≥ 14 days after vaccination
Presence of the first episode of RSV-ARD (RSV A and/or RSV B) ≥ 14 days after vaccination
Number of participants experiencing RSV-ARD (RSV A and/or RSV B) ≥ 14 days after vaccination
Time frame: ≥ 14 days after vaccination
Presence of the first episode of RSV MAARD (RSV A and/or RSV B) ≥ 14 days after vaccination
Number of participants experiencing RSV-MAARD (RSV A and/or RSV B) ≥ 14 days after vaccination
Time frame: ≥ 14 days after vaccination
Presence of the first episode of RSV LRTD (RSV A) occurring ≥ 14 days after vaccination)
Number of participants experiencing RSV-LRTD (RSV A) ≥ 14 days after vaccination
Time frame: ≥ 14 days after vaccination
Presence of the first episode of RSV LRTD (RSV B) occurring ≥ 14 days after vaccination
Number of participants experiencing RSV-LRTD (RSV B) ≥ 14 days after vaccination
Time frame: ≥ 14 days after vaccination
Presence of the first episode of RSV-LRTD (RSV A and/or RSV B and by each one) by age group
Number of participants experiencing RSV-LRTD (RSV A and/or B and by each one) by age group
Time frame: ≥ 14 days after vaccination
Presence of the first episode of RSV LRTD (RSV A and/or RSV B and by each one) by baseline comorbidities
Number of participants experiencing RSV-LRTD (RSV A and/or B and by each one) by baseline comorbidities
Time frame: ≥ 14 days after vaccination
Presence of the first episode of RSV LRTD (RSV A and/or RSV B and by each one) by baseline frailty status
Number of participants experiencing RSV-LRTD (RSV A and/or B and by each one) by baseline frailty status
Time frame: ≥ 14 days after vaccination
Presence of hospitalization due to RSV-ARD and/or RSV-LRTD
Number of participants hospitalized due to RSV-ARD and/or RSV-LRTD
Time frame: ≥ 14 days after vaccination
Duration (number of days) of RSV LRTD episodes (RSV A and/or RSV B)
Duration (number of days) of RSV LRTD episodes (RSV A and/or RSV B)
Time frame: ≥ 14 days after vaccination
Duration (number of days) of RSV ARD episodes (RSV A and/or RSV B)
Duration (number of days) of RSV ARD episodes (RSV A and/or RSV B)
Time frame: ≥ 14 days after vaccination
Presence of the first episode of severe RSV LRTD (RSV A and/or RSV B and by each one) occurring ≥ 14 days after vaccination
Number of participants experiencing severe RSV-LRTD (RSV A and/or B and by each one)
Time frame: ≥ 14 days after vaccination
RSV A serum neutralizing antibodies (nAb) titers at pre vaccination (D01) and 28 days (D29) post vaccination in the Immunogenicity Subset
RSV A serum neutralizing antibodies (nAb) titers at pre vaccination (D01) and 28 days (D29) post vaccination in the Immunogenicity Subset
Time frame: Day 1 and Day 29
RSV B serum nAb titers at pre vaccination (D01) and 28 days (D29) post vaccination in the Immunogenicity Subset
RSV B serum nAb titers at pre vaccination (D01) and 28 days (D29) post vaccination in the Immunogenicity Subset
Time frame: Day 1 and Day 29
Serum anti-F immunoglobulin G (IgG) antibody (Ab) titers at pre-vaccination (D01) and 28 days (D29) post vaccination in the Immunogenicity Subset
Serum anti-F immunoglobulin G (IgG) antibody (Ab) titers at pre-vaccination (D01) and 28 days (D29) post vaccination in the Immunogenicity Subset
Time frame: Day 1 and Day 29
RSV A serum nAb titers at 6 months post-vaccination in the Immunogenicity Subset
RSV A serum nAb titers at 6 months post-vaccination in the Immunogenicity Subset
Time frame: Month 6
RSV B serum nAb titers at 6 months post-vaccination in the Immunogenicity Subset
RSV B serum nAb titers at 6 months post-vaccination in the Immunogenicity Subset
Time frame: Month 6
Serum anti-F IgG Ab titers at 6 months post-vaccination in the Immunogenicity Subset
Serum anti-F IgG Ab titers at 6 months post-vaccination in the Immunogenicity Subset
Time frame: Month 6
Presence of solicited injection site or systemic reactions
Number of participants reporting: * injection site reactions: pain, erythema and swelling * systemic reactions: fever, headache, fatigue, myalgia, arthralgia and chills
Time frame: Within 7 days after primary vaccination
Presence of unsolicited immediate systemic adverse events (AEs)
Number of participants experiencing an unsolicited immediate systemic adverse event
Time frame: Within 30 minutes after primary vaccination
Presence of unsolicited AEs
Number of participants experiencing unsolicited AEs
Time frame: Within 28 days after primary vaccination
Presence of serious adverse events (SAEs)
Number of participants experiencing SAEs
Time frame: Throughout study (approximately 6 months)
Presence of medically attended adverse events (MAAEs)
Number of participants experiencing MAAEs
Time frame: Throughout study (approximately 6 months)
Presence of adverse events of special interest (AESIs)
Number of participants experiencing AESIs
Time frame: Throughout study (approximately 6 months)
Plan to share: Yes — 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
Ran from Apr 2024 to primary completion in Mar 2025, 11 months.
Of 32 industry-sponsored phase 2 interventional studies under Respiratory Syncytial Virus Infections, half reached primary completion within 11 months of starting (the median), counting those still running; a quarter within 5 and three quarters within 27. This study's 11 months is close to that.
Counting every sponsor, half of 37 studies reached it within 11 months; a quarter within 5 and three quarters within 27.
How these figures are worked out, and which studies are left out of them.
This study is completed, as verified in Mar 2026. You cannot join it, but the record below documents what was studied.
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Respiratory Syncytial Virus Infections →
Sanofi Pasteur, a Sanofi Company →