Intranasal Challenge of Healthy Adults With Respiratory Syncytial Virus (RSV)

The primary objective is to evaluate the suitability of the challenge model in measuring the efficacy of MEDI-557 compared to placebo in healthy adult participants for the reduction in the incidence of RSV through 12 days post-RSV challenge with the RSV Memphis-37 strain.

This is designed to be a double-blind, placebo-controlled, randomized study. Approximately 30 participants will be randomized, dosed and followed. Participants will be randomly assigned to receive a single intravenous (IV) dose of MEDI-557 or placebo. Participants will be inoculated with RSV-A. Participants will be followed for efficacy for 12 days post-RSV challenge. Safety follow-up will be approximately 12 months from randomization.

Eligibility Criteria:
Inclusion Criteria:

1. Healthy as determined by medical history and physical examination.
2. Age 19 through 38 years at the time of screening.
3. Written informed consent and any locally required authorization obtained from the subject prior to performing any protocol-related procedures, including screening evaluations.
4. Weight less than or equal to (\<=) 10 kilogram (kg) with body mass index (BMI) less than (\<) 32 kilogram per meter square (kg/m\^2).
5. Normotensive (systolic blood pressure \[BP\] \<150 millimeters of mercury (mmHg) and diastolic BP \< 90 mmHg).
6. Females of childbearing age using contraception.
7. Males who are sexually active with a female partner of childbearing potential, using contraception.
8. Sero-suitable (that is, low serum RSV neutralizing antibody titre) for RSV infection.

Exclusion Criteria:

Current medical conditions as follows:

1. Clinical evidence of chronic pulmonary disease or any use of a bronchodilator or other asthma medication.
2. Current smoker unwilling/unable to desist for the quarantine phase of the study.
3. History or clinical evidence of recurrent lower respiratory tract infection.
4. Evidence of infection with hepatitis A, B, or C virus or human immunodeficiency virus (HIV) by serology.

   Medical history as follows:
5. History of immunodeficiency.
6. History of chronic sinusitis.
7. History of frequent epistaxis.
8. History of or current diagnosis of diabetes.
9. Prior/concomitant therapy including

   * Receipt of any systemic chemotherapeutic agent at any time;
   * Receipt of systemic glucocorticoids within 1 month, or any other immunosuppressive drug within 6 months prior to challenge.
   * Receipt of any investigational drug within 6 months prior to dose or concurrent enrolment in another clinical study.
   * Prior participation in a clinical trial of any experimental RSV viral challenge delivered directly to the respiratory tract at any time, or any other respiratory virus challenge within 1 year prior to dose.
10. Nursing mother.
11. Alcohol or drug addiction/abuse within the past 2 years.
12. A positive urine Class A drug or alcohol screen unless there is a medical reason.
13. History of seasonal hay fever or seasonal allergies.
14. Employees of the clinical study site or sponsor, any other individuals involved with the conduct of the study, or immediate family members of such individuals.
15. Health care workers anticipated to have patient contact within 2 weeks after viral challenge.
16. Participants who, for an additional 2 weeks after discharge from the isolation facility, are likely to have contact with a household member or close contact with someone who is: (a) less than 3 years of age; (b) any person with any known immunodeficiency; (c) any person receiving immunosuppressant medications; (d) any person undergoing or soon to undergo cancer chemotherapy within 28 days of challenge; (e) any person who has diagnosed emphysema or COPD, is elderly residing in a nursing home, or with severe lung disease or medical condition; or (f) any person who has received a transplant (bone marrow or solid organ).
17. As a result of the medical interview, physical examination, or screening investigations, the investigator(s) considers the participant unfit for the study.