A Study to Learn About the Vaccine RSVpreF In Pregnant Participants With HIV and Their Infants

The purpose of the study is to learn about the safety and immune activity of the RSVpreF vaccine. It will be studied in infants born to mothers living with HIV. These infants may have higher chances of getting sick or dying due to RSV infection. Respiratory Syncytial Virus (RSV) is a common type of virus (germ) that can cause severe illness (airway diseases), where medical help is needed. Vaccines help your body make antibodies which help fight against diseases. The antibodies are substances your body uses to fight off an infection. The antibodies can be passed to the infant through the placenta of the mother.

The study will look at the safety, tolerability, and immune activity in mothers and their infants.

This study is seeking pregnant women who are:

* Less than or equal to 49 years old and have HIV (Human immunodeficiency virus -
* Receiving standard medical care during the pregnancy
* Do not have syphilis (bacterial sexually transmitted disease), Hepatitis B Virus ((HBV) liver infection), Tuberculosis ((TB) bacterial lung infection).
* Have been on stable (anti-retroviral) HIV treatment for more than or equal to 90 days.
* agree to be present for all study visits, procedures, and blood draws.

Participants will either receive:

* RSVpreF vaccine
* A placebo. A placebo does not have any medicine it but looks just like the study vaccine.

Pregnant participants will be involved in the study from:

* consent during their current pregnancy, and
* for 6 months after delivery of their baby (around 10 months in total). Pregnant participants will have at least 5 planned visits in this study. Infant participants: All eligible babies born to enrolled mothers will be followed up from birth for up to 6 months. Infant participants will have at least 3 study visits, with some site visits allowed to happen via home visits or over the telephone.


Eligibility Criteria:
Key Inclusion Criteria - Maternal Participants

* Women ≤49 years of age who are between 24 0/7 and 36 0/7 weeks of gestation on the day of planned vaccination, with an uncomplicated singleton pregnancy who are at no known increased risk for complications.
* Confirmed stable HIV disease.
* Current and stable use of antiretroviral therapy(ART) for at least 90 days prior to enrolment.
* Had a fetal anomaly ultrasound examination performed at ≥18 weeks of pregnancy with no significant fetal abnormalities observed.
* Intention to deliver at a hospital or birthing facility where study procedures can be obtained.
* Participant is willing to give informed consent for the participant's infant to participate in the study.
* Capable of giving signed informed consent, which includes compliance with the requirements and restrictions listed in the informed consent document (ICD) and in this protocol.

Key Inclusion Criteria - Infant Participants

* Evidence of a signed and dated ICD, signed by the parent(s)/legal guardian(s).
* Parent(s)/legal guardian(s) willing and able to comply with scheduled visits, investigational plan, laboratory tests, and other study procedures

Key Exclusion Criteria - Maternal Participants

* Prepregnancy body mass index (BMI) of \>40 kg/m2 . If prepregnancy BMI is not available, the BMI at the time of the first obstetric visit during the current pregnancy may be used.
* Participant with opportunistic infections or malignancy.
* History of active chronic viral hepatitis with biochemical evidence of aspartate aminotransferase (AST) or alanine aminotransferase (ALT) values \>5 times the upper limit of normal within 6 months before enrollment.
* History of severe adverse reaction associated with a vaccine and/or severe allergic reaction (eg, anaphylaxis) to any component of the study intervention or any related vaccine.
* Current pregnancy resulting from in vitro fertilization. Participants known to have used clomiphene citrate and/or letrozole with or without intrauterine insemination (IUI) are permitted.
* Current pregnancy complications or abnormalities at the time of consent that will increase the risk associated with the participation in and completion of the study, including but not l limited to the following:
* Preeclampsia, eclampsia, or uncontrolled gestational hypertension.
* Placental abnormality.
* Polyhydramnios or oligohydramnios.
* Significant bleeding or blood clotting disorder.
* Endocrine disorders, including untreated hyperthyroidism or untreated hypothyroidism. This also includes disorders of glucose intolerance (eg, diabetes mellitus type 1 or 2) antedating pregnancy or occurring during pregnancy if uncontrolled at the time of consent.
* Any signs of premature labor with the current pregnancy or having ongoing intervention (medical/surgical) in the current pregnancy to prevent preterm birth.
* Prior pregnancy complications or abnormalities at the time of consent, based on the investigator's judgment, that will increase the risk associated with the participation in and completion of the study, including but not limited to the following:
* Prior preterm delivery at ≤34 weeks' gestation
* Prior stillbirth or neonatal death
* Previous infant with a known genetic disorder or significant congenital anomaly
* Non-HIV-associated congenital or acquired immunodeficiency disorder, or rheumatologic disorder or other illness requiring chronic treatment with known immunosuppressant medications.
* Antituberculosis treatment use currently or at any time during this current pregnancy.

Key Exclusion Criteria - Infant Participants

• Infant who is a direct descendant (eg, child or grandchild) of the investigator site staff or sponsor and sponsor delegate employees directly involved in the conduct of the study.