Trial Outcomes & Findings for Study of a Respiratory Syncytial Virus Candidate Encapsulated in a Lipid Nanoparticle Based Formulation in Adults Aged 18 to 50 Years and 60 Years and Older (NCT NCT05639894)

This study was conducted at 28 centers in 3 countries between 17 November 2022 to 02 May 2025. 790 participants were enrolled in Stage 1 (Sentinel and Main Cohort) and 75 participants were enrolled in Stage 2.

A total of 865 unique participants were enrolled in the study. 129 eligible participants from the Stage 1: Main Cohort were included in the Stage 1: Booster Cohort because these assessed separate objectives. Dose groups are defined by combinations of dose level (A to D) and formulation type, with dose levels increasing from A (lowest) to D (highest) in each Stage.

Study of a Respiratory Syncytial Virus Candidate Encapsulated in a Lipid Nanoparticle Based Formulation in Adults Aged 18 to 50 Years and 60 Years and Older

An AE was any untoward medical occurrence in a clinical study participant, temporally associated with the use of study vaccine, whether or not considered related to the study vaccine. Immediate events were recorded to capture medically relevant unsolicited systemic AEs which occurred within the first 30 minutes after vaccination. An unsolicited AE was an observed AE that did not fulfill the conditions of solicited reactions, i.e., pre-listed in the case report form (CRF) in terms of diagnosis and onset window post-vaccination.

An injection site reaction was an adverse reaction (AR) at and around the injection site of the study vaccine. Injection site reactions were commonly inflammatory reactions. Solicited injection site reactions were reactions at and around the injection site of the study vaccine observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRF. Solicited systemic reactions were systemic AEs observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRF. Solicited reactions were considered to be related to the study vaccine administered.

An AE was any untoward medical occurrence in a clinical study participant, temporally associated with the use of study vaccine, whether or not considered related to the study vaccine. An unsolicited AE was an observed AE that did not fulfill the conditions of solicited reactions, i.e., pre-listed in the CRF in terms of diagnosis and onset window post-vaccination.

An MAAE was a new-onset or a worsening of a condition that prompted the participant to seek unplanned medical advice at a physician's office or Emergency Department.

An MAAE was a new-onset or a worsening of a condition that prompted the participant to seek unplanned medical advice at a physician's office or Emergency Department.

An AE was any untoward medical occurrence in a clinical study participant, temporally associated with the use of study vaccine, whether or not considered related to the study vaccine. An SAE was defined as any AE that at any dose resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, was a congenital anomaly/birth defect, or was an important medical event. An AESI (serious or non-serious) was 1 of scientific and medical concern specific to the Sponsor's study vaccine or program, for which ongoing monitoring and rapid communication by the investigator to the Sponsor was appropriate.

Clinical evaluation of laboratory parameters (hematology, clinical chemistry and coagulation parameters) was performed to determine out-of-range values (below or above normal range). Number of participants with a shift from baseline to out-of-range value within 7 days after primary vaccination (Day 8) are reported. Laboratory parameters with a notable shift from baseline included: hematology: hemoglobin, white blood cells (WBC), red blood cells (RBC); clinical chemistry: blood urea nitrogen (BUN), potassium, glucose, C-reactive protein (CRP), direct bilirubin, troponin I; and coagulation parameters: partial thromboplastin time (PTT).

Neutralizing antibodies activity against RSV A was measured using the RSV plaque reduction neutralization test (PRNT) (micro-PRNT). RSV A serum neutralizing antibodies titers were expressed as 1/dilution.

Neutralizing antibodies activity against RSV A and RSV B was measured using the RSV PRNT (micro-PRNT). RSV A and RSV B serum neutralizing antibodies titers were expressed as 1/dilution.

An AE was any untoward medical occurrence in a clinical study participant, temporally associated with the use of study vaccine, whether or not considered related to the study vaccine. Immediate events were recorded to capture medically relevant unsolicited systemic AEs which occurred within the first 30 minutes after vaccination. An unsolicited AE was an observed AE that did not fulfill the conditions of solicited reactions, i.e., pre-listed in the CRF in terms of diagnosis and onset window post-vaccination.

An injection site reaction was an AR at and around the injection site of the study vaccine. Injection site reactions were commonly inflammatory reactions. Solicited injection site reactions were reactions at and around the injection site of the study vaccine observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRF. Solicited systemic reactions were systemic AEs observed and reported under the conditions (nature and onset) pre-listed in the protocol and CRF. Solicited reactions were considered to be related to the study vaccine administered.

An AE was any untoward medical occurrence in a clinical study participant, temporally associated with the use of study vaccine, whether or not considered related to the study vaccine. An unsolicited AE was an observed AE that did not fulfill the conditions of solicited reactions, i.e., pre-listed in the CRF in terms of diagnosis and onset window post-vaccination. An MAAE was a new-onset or a worsening of a condition that prompted the participant to seek unplanned medical advice at a physician's office or Emergency Department.

An AE was any untoward medical occurrence in a clinical study participant, temporally associated with the use of study vaccine, whether or not considered related to the study vaccine. An SAE was defined as any AE that at any dose resulted in death, was life-threatening, required inpatient hospitalization or prolongation of existing hospitalization, resulted in persistent or significant disability/incapacity, was a congenital anomaly/birth defect, or was an important medical event. An AESI (serious or non-serious) was 1 of scientific and medical concern specific to the Sponsor's study vaccine or program, for which ongoing monitoring and rapid communication by the investigator to the Sponsor was appropriate.

Clinical evaluation of laboratory parameters (hematology and clinical chemistry) was performed to determine out-of-range values (below or above normal range). Number of participants with a shift from baseline to out-of-range value within 7 days after booster vaccination (Month 12 + 7 days) are reported. Laboratory parameters with a notable shift from baseline included: hematology: RBC; clinical chemistry: potassium, glucose, direct bilirubin.

Neutralizing antibodies activity against RSV A was measured using the RSV PRNT (micro-PRNT). RSV A serum neutralizing antibodies titers were expressed as 1/dilution.

Binding antibodies activity against RSV anti-F IgG was measured using enzyme-linked immunosorbent assay (ELISA). Geometric mean concentrations were expressed as endotoxin units per milliliter (EU/mL).

Neutralizing antibodies activity against RSV A was measured using the RSV PRNT (micro-PRNT). RSV A serum neutralizing antibodies titers were expressed as 1/dilution.

Binding antibodies activity against RSV anti-F IgG was measured using ELISA. Geometric mean concentrations were expressed as EU/mL.

Binding antibodies activity against RSV anti-F IgG was measured using ECL assay. Geometric mean concentrations were expressed as arbitrary units (AU)/mL.