The purpose of this study is to evaluate the efficacy, safety, pharmacokinetics (PK), and antidrug antibody (ADA) response for MEDI8897 in healthy late preterm and term infants who are 35 weeks or greater gestational age and entering their first RSV season.

This pivotal Phase 3 study will determine if MEDI8897 will prevent medically attended RSV-confirmed lower respiratory tract infections (LRTI) in healthy infants entering their first RSV season. The population to be enrolled is healthy late preterm and term infants born 35 weeks 0 days or greater gestational age (GA) who would not be eligible to receive RSV prophylaxis. A total of approximately 3,000 infants will be randomized 2:1 to receive either MEDI8897 or placebo. All subjects will be followed for approximately 510 days after dosing. Enrollment is planned at approximately 350 sites across the USA, Canada, Europe, Asia, and Southern Hemisphere.

Key Inclusion Criteria:

• Healthy infants in their first year of life and born at or after 35 weeks 0 days GA
• Infants who are entering their first RSV season at the time of screening

Key Exclusion Criteria:

• Meets national or other local criteria to receive commercial palivizumab
• Any fever (≥ 100.4°F [≥ 38.0°C], regardless of route) or acute illness within 7 days prior to randomization
• Active RSV infection (a child with signs/symptoms of respiratory infection must have negative RSV testing) or known prior history of RSV infection
• Receipt of palivizumab or other RSV monoclonal antibody or any RSV vaccine, including maternal RSV vaccination

Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal. All request will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA Pharma Data Sharing Principles. For details of our timelines, please rerefer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

When a request has been approved AstraZeneca will provide access to the de-identified individual patient-level data in an approved sponsored tool . Signed Data Sharing Agreement (non-negotiable contract for data accessors) must be in place before accessing requested information. Additionally, all users will need to accept the terms and conditions of the SAS MSE to gain access. For additional details, please review the Disclosure Statements at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.