An RSV-associated LRTI of any severity was characterized by a history of cough OR difficulty in breathing, AND a blood oxygen saturation by pulse oximetry (SpO2) lower than (<) 95%, OR respiratory rate increase AND a confirmed RSV infection. An RSV-associated severe LRTI met the case definition of RSV-LRTI AND was additionally characterized by a SpO2 <93%, OR lower chest wall in-drawing, OR inability to feed, OR failure to respond/unconscious. Medically assessed = the infant was evaluated by a healthcare professional for the LRTI.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed set who were born after at least 4 weeks of their maternal participants vaccination.

An SAE is defined as any untoward medical occurrence that resulted in death, was life-threatening, required hospitalization or prolongation of existing hospitalization, resulted in disability/incapacity, was a congenital anomaly/birth defect or resulted in other situations that were considered serious per medical or scientific judgment. At least one SAE = occurrence of at least one SAE regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for infants, which included the infants live-born to exposed maternal participants, whose parents/legally acceptable representative(s) (LARs) completed the informed consent process and signed the informed consent form.

A participant was considered a 'withdrawal' from the study when no study procedure has occurred, no follow-up has been performed and no further information has been collected for this participant from the date of withdrawal/last contact. Participants who were withdrawn from the study because of AEs were clearly distinguished from participants who were withdrawn for other reasons. Investigators followed participants who were withdrawn from the study as a result of an AE until the event was resolved. At least one AE leading to study withdrawal = occurrence of at least one AE leading to study withdrawal regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for infants, which included the infants live-born to exposed maternal participants, whose parents/legally acceptable representative(s) (LARs) completed the informed consent process and signed the informed consent form.

An MAE is defined as an unsolicited AE, such as a symptom or illness, which required hospitalization, or emergency room visit, or visit to/by a health care provider. At least one MAE = occurrence of at least one MAE regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for infants, which included the infants live-born to exposed maternal participants, whose parents/legally acceptable representative(s) (LARs) completed the informed consent process and signed the informed consent form.

An SAE is defined as any untoward medical occurrence that resulted in death, was life-threatening, required hospitalization or prolongation of existing hospitalization, resulted in disability/incapacity, was a congenital anomaly/birth defect or resulted in other situations that were considered serious per medical or scientific judgment. At least one SAE = occurrence of at least one SAE regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for infants, which included the infants live-born to exposed maternal participants, whose parents/LARs completed the informed consent process and signed the informed consent form.

A participant was considered a 'withdrawal' from the study when no study procedure has occurred, no follow-up has been performed and no further information has been collected for this participant from the date of withdrawal/last contact. Participants who were withdrawn from the study because of AEs were clearly distinguished from participants who were withdrawn for other reasons. Investigators followed participants who were withdrawn from the study as a result of an AE until the event was resolved. At least one AE leading to study withdrawal = occurrence of at least one AE leading to study withdrawal regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for infants, which included the infants live-born to exposed maternal participants, whose parents/LARs completed the informed consent process and signed the informed consent form.

An MAE is defined as an unsolicited AE, such as a symptom or illness, which required hospitalization, or emergency room visit, or visit to/by a health care provider. At least one MAE = occurrence of at least one MAE regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for infants, which included the infants live-born to exposed maternal participants, whose parents/LARs completed the informed consent process and signed the informed consent form.

RSV-associated hospitalization is defined as a confirmed RSV infection and hospitalized for acute medical condition. Hospitalization is defined as admission for observation or treatment based on the judgment of a health care provider.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

All-cause LRTI was characterized by history of cough OR difficulty in breathing, AND SpO2 < 95%, OR respiratory rate increase.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all the infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

All-cause LRTI was characterized by history of cough OR difficulty in breathing, AND SpO2 < 95%, OR respiratory rate increase. Hospitalization is defined as admission for observation or treatment based on the judgment of a health care provider.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

An RSV-associated LRTI of any severity was characterized by a history of cough OR difficulty in breathing, AND an SpO2 <95%, OR respiratory rate increase AND a confirmed RSV infection. An RSV-associated severe LRTI met the case definition of RSV-LRTI AND was additionally characterized by an SpO2 <93%, OR lower chest wall in-drawing, OR inability to feed, OR failure to respond/unconscious. Medically assessed = the infant was evaluated by a healthcare professional for the LRTI.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

An RSV-associated LRTI of any severity was characterized by a history of cough OR difficulty in breathing, AND an SpO2 <95%, OR respiratory rate increase AND a confirmed RSV infection. Medically assessed = the infant was evaluated by a healthcare professional for the LRTI.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

An RSV-associated LRTI of any severity was characterized by a history of cough OR difficulty in breathing, AND an SpO2 <95%, OR respiratory rate increase AND a confirmed RSV infection. An RSV-associated severe LRTI met the case definition of RSV-LRTI AND was additionally characterized by an SpO2 <93%, OR lower chest wall in-drawing, OR inability to feed, OR failure to respond/unconscious. Medically assessed = the infant was evaluated by a healthcare professional for the LRTI. The RSV subtypes assessed for this analysis were RSV subtype A and RSV subtype B.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants which included all the infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

An RSV-associated LRTI of any severity was characterized by a history of cough OR difficulty in breathing, AND an SpO2 <95%, OR respiratory rate increase AND a confirmed RSV infection. Medically assessed = the infant was evaluated by a healthcare professional for the LRTI. The RSV subtypes assessed for this analysis were RSV subtype A and RSV subtype B.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

An RSV-associated LRTI of any severity was characterized by a history of cough OR difficulty in breathing, AND an SpO2 <95%, OR respiratory rate increase AND a confirmed RSV infection. An RSV-associated severe LRTI met the case definition of RSV-LRTI AND was additionally characterized by an SpO2 <93%, OR lower chest wall in-drawing, OR inability to feed, OR failure to respond/unconscious. Medically assessed = the infant was evaluated by a healthcare professional for the LRTI.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

An RSV-associated LRTI of any severity was characterized by a history of cough OR difficulty in breathing, AND an SpO2 <95%, OR respiratory rate increase AND a confirmed RSV infection. Medically assessed = the infant was evaluated by a healthcare professional for the LRTI.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

The number of infant participants with all-cause pneumonia is presented in this outcome measure.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

RSV-associated hospitalization is defined as a confirmed RSV infection and hospitalized for acute medical condition. Hospitalization is defined as admission for observation or treatment based on the judgment of a health care provider.

The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

RSV-associated MA-RTI is defined as a medically attended visit for RTI symptoms and confirmed RSV infection.

The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

RSV-A neutralizing titers were determined by neutralization assay and expressed as geometric mean titers (GMTs).

The analysis was performed on the Per Protocol - Immunogenicity set for maternal participants, which included all maternal participants who received the study intervention to which they were randomized and had post-vaccination immunogenicity data available for the specified analysis at each of the specified time points (i.e. Day 1, Day 31, delivery) minus those participants with protocol deviations that led to exclusion.

RSV-A neutralizing titers were determined by neutralization assay and expressed as GMTs. The titers were measured on the cord blood sample collected at delivery, or on a blood sample collected from the infant within 72 hours after birth (if no cord blood sample could be obtained).

The analysis was performed on the Per Protocol - Immunogenicity set for infants, which included all infant participants in the Exposed set who had post-delivery/birth immunogenicity data available for the specified analysis at the specified time points (i.e. at delivery or within 72 hours after birth), minus those who (a) were born less than 4 weeks post- maternal participant vaccination and/ or (b) had protocol deviations that led to exclusion.

RSV-A neutralizing titers were determined by neutralization assay and expressed as GMTs.

The analysis was performed on a sub-cohort from the Per Protocol - Immunogenicity set for infants, which included the infant participants for whom blood samples were collected for the specified analysis at Day 43 post-birth.

RSV-A neutralizing titers were determined by neutralization assay and expressed as GMTs.

The analysis was performed on a sub-cohort from the Per Protocol - Immunogenicity set for infants, which included the infant participants for whom blood samples were collected for the specified analysis at Day 121 post-birth.

RSV-A neutralizing titers were determined by neutralization assay and expressed as GMTs.

The analysis was performed on a sub-cohort from the Per Protocol - Immunogenicity set for infants, which included the infant participants for whom blood samples were collected for the specified analysis at Day 181 post-birth.

RSV MAT IgG-specific antibody concentrations were determined by enzyme-linked immunosorbent assay (ELISA) and expressed as geometric mean concentrations (GMCs) in ELISA units per milliliter (ELU/mL).

The analysis was performed on the Per Protocol - Immunogenicity set for maternal participants, which included all maternal participants who received the study intervention to which they were randomized and had post-vaccination immunogenicity data available for the specified analysis at the specified time point (i.e. delivery) minus those participants with protocol deviations that led to exclusion.

RSV MAT IgG-specific antibody concentrations were determined by ELISA and expressed as GMCs in ELU/mL. The antibody concentrations were measured on the cord blood sample collected at delivery, or on a blood sample collected from the infant within 72 hours after birth (only if no cord blood sample could be obtained at delivery).

The analysis was performed on the Per Protocol - Immunogenicity set for infants, which included all infant participants in the Exposed set who had post-delivery/birth immunogenicity data available for the specified analysis at the specified time points (i.e. at delivery or within 72 hours after birth), minus those who (a) were born less than 4 weeks post-maternal participant vaccination and/ or (b) had protocol deviations that led to exclusion.

The placental transfer ratio of RSV-MAT IgG-specific antibody concentration was determined from cord blood over that of the blood sample from mother at delivery. If no cord blood could be obtained, an infant blood sample was collected 72 hours after birth.

The analysis was performed on all pairs of maternal participants (from Per Protocol -Immunogenicity set for maternal participants) and their infants (from Per Protocol - Immunogenicity set for infants) with available results for this outcome measure at the specified time points.

Assessed solicited administration site events included erythema, pain and swelling at the injection site. Any pain = occurrence of the symptom regardless of intensity grade. Any erythema and swelling = symptom reported with a surface diameter greater than or equal to 20 millimeters.

The analysis was performed on the Solicited Safety set for maternal participants, which included all maternal participants who received the study intervention and who had solicited safety data available during the specified period (i.e. from Day 1 to Day 7 included).

Assessed solicited systemic events included abdominal pain, diarrhea, fatigue, headache, nausea, fever [temperature equal to or above (>=) 38 degrees Celsius (°C)/100.4 degrees Fahrenheit (°F), regardless of the location of measurement] and vomiting. Any = occurrence of the adverse event regardless of intensity grade or relation to study vaccination.

The analysis was performed on the Solicited Safety set for maternal participants, which included all maternal participants who received the study intervention and who had solicited safety data available during the specified period (i.e. from Day 1 to Day 7 included).

An unsolicited AE is defined as any AE reported in addition to those solicited during the clinical study. Also, any 'solicited' symptom with onset outside the specified period of follow-up for solicited symptoms was reported as an unsolicited AE. Any = occurrence of any unsolicited AE regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

An SAE is defined as any untoward medical occurrence that resulted in death, was life-threatening, required hospitalization or prolongation of existing hospitalization, resulted in disability/incapacity, was a congenital anomaly/birth defect in the offspring of a study participant or resulted in abnormal pregnancy outcomes or in other situations that were considered serious per medical or scientific judgment. At least one SAE = occurrence of at least one SAE regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

A participant was considered a 'withdrawal' from the study when no study procedure has occurred, no follow-up has been performed and no further information has been collected for this participant from the date of withdrawal/last contact. Participants who were withdrawn from the study because of AEs were clearly distinguished from participants who were withdrawn for other reasons. Investigators followed participants who were withdrawn from the study as a result of an AE until the event was resolved. At least one AE leading to study withdrawal = occurrence of at least one AE leading to study withdrawal regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

All-cause MA-RTI occurred when the maternal participant visited a healthcare professional (e.g., a General Practitioner) for any respiratory symptom, including (but not limited to) cough, sore throat, sputum production and difficulty breathing. At least one all-cause MA-RTI = occurrence of at least one all-cause MA-RTI regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

An MAE is defined as an unsolicited AE, such as a symptom or illness, which required hospitalization, or emergency room visit, or visit to/by a health care provider. At least one MAE = occurrence of at least one MAE regardless of intensity grade or relation to vaccination.

The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

Assessed pregnancy outcomes included live birth with no congenital anomalies, live birth with minor congenital anomaly(ies), live birth with at least 1 major congenital anomaly, fetal death/still birth with no congenital anomalies, fetal death/still birth with at least 1 major congenital anomaly and unknown outcome (includes participants withdrawn before/at delivery with no available data of pregnancy outcomes).

The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

Pregnancy-related AESIs included chorioamnionitis, fetal growth restriction, gestational diabetes mellitus, gestational hypertension, pre-eclampsia, pre-eclampsia with severe features including eclampsia, maternal death, premature preterm rupture of membranes, preterm labor, provider-initiated preterm birth.

The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

Neonatal/infant AESIs included congenital anomalies with functional defects, congenital anomalies with internal structural defects, congenital anomalies with major external structural defects, extremely low birth weight (<1000 grams), low birth weight (<2500 grams), very low birth weight (<1500 grams), neonatal death in a preterm live birth (gestational age >=28 and <37 weeks), neonatal death in a term live birth (>=37 weeks of gestational age), neonatal death in an extremely pre-term birth (gestational age >=22 and <28 weeks), preterm birth (<37 weeks of gestational age), small for gestational age.

The analysis was performed on the Exposed Set for infants, which included infants live-born to exposed maternal participants, whose parents/LARs completed the informed consent process and signed the informed consent form.