A Phase III Study to Assess the Lot-to-lot Consistency of GSK's Investigational RSV Maternal Vaccine and the Immune Response and Safety of RSV Maternal Vaccine When Given Alone or Co-administered With GSK's Influenza D-QIV Vaccine in Healthy Non-pregnant Women.

The purpose of this study is to evaluate the clinical lot-to-lot consistency of the respiratory syncytial virus (RSV) maternal (RSV MAT) vaccine administered to healthy non-pregnant women 18-49 years of age (YOA). In addition, this study will evaluate immunogenicity, safety and reactogenicity from co-administration of RSV MAT vaccine and GSK's quadrivalent seasonal influenza (Flu D-QIV) vaccine.


Eligibility Criteria:
Inclusion Criteria:

* Participants who, in the opinion of the investigator, can and will comply with the requirements of the protocol.
* Written or witnessed/thumb printed informed consent obtained from the participant prior to performance of any study specific procedure.
* Healthy female participants; as established by medical history and clinical examination, aged 18 to 49 years at the time of the first study intervention administration.

  * Female participants of childbearing potential may be enrolled in the study, if the participant:
  * has practiced adequate contraception for 1 month prior to study intervention administration, and
  * has a negative pregnancy test on the day of study intervention administration, and
  * has agreed to continue adequate contraception during the entire treatment period and for 1 month after completion of the study intervention administration.
* No local condition precluding injection in both left and right deltoid muscles.

Exclusion Criteria:

Medical conditions

* History of any reaction or hypersensitivity likely to be exacerbated by any component of the study interventions;
* Any confirmed or suspected immunosuppressive or immunodeficient condition, based on medical history and physical examination;
* Current autoimmune disorder, for which the participant has received immune-modifying therapy within 6 months, before study vaccination;
* Hypersensitivity to latex;
* Acute or chronic clinically significant abnormality or poorly controlled pre-existent co-morbidities or any other clinical conditions, as determined by physical examination or medical history that, in the opinion of the investigator, might pose additional risk to the participant due to participation in the study;
* Significant or uncontrolled psychiatric illness;
* Recurrent history or uncontrolled neurological disorders or seizures;
* Documented HIV-positive participant;
* Body mass index \> 40 kg/m\^2;
* Any clinically significant\* hematological parameter and/or biochemical laboratory abnormality.

  \*The investigator should use his/her clinical judgment to decide which abnormalities are clinically significant.
* Any other clinical condition that, in the opinion of the investigator, might pose additional risk to the participant due to participation in the study.

Prior/Concomitant therapy

* Use of any investigational or non-registered product other than the study intervention(s) during the period starting 30 days before study intervention (Day -29 to Day 1), or planned use during the study period;
* Administration of long-acting immune-modifying drugs at any time during the study period;
* Administration of immunoglobulins and/or any blood products or plasma derivatives during the period starting 3 months before the study intervention or planned administration during the study period;
* Chronic administration of immunosuppressants or other immune-modifying drugs during the period starting 3 months prior to the first study intervention dose(s). For corticosteroids, this will mean prednisone 5 mg/day, or equivalent. Inhaled and topical steroids are allowed;
* Planned administration/administration of a vaccine not foreseen by the study protocol within the period starting 30 days before and ending 30 days after the vaccination dose;
* Administration of a seasonal influenza vaccine during the 6 months preceding entry into the study;
* Previous experimental vaccination against RSV.

Prior/Concurrent clinical study experience Concurrently participating in another clinical study, at any time during the study period, in which the participant has been or will be exposed to an investigational or a non-investigational vaccine/product;

Other exclusions

* Pregnant or lactating female;
* Female planning to become pregnant or planning to discontinue contraceptive precautions;
* Alcoholism or substance use disorder within the past 24 months based on the presence of two or more of the following abuse criteria: hazardous use, social/interpersonal problems related to use, neglected major roles to use, withdrawal tolerance, use of larger amounts or longer, repeated attempts to quit or control use, much time spent using, physical or psychological problems related to use, activities given up to use, craving;
* Any study personnel or their immediate dependents, family, or household members.