Study to Evaluate the Safety of MEDI-534 Vaccine Against Respiratory Syncytial Virus (RSV) and Parainfluenza Virus Type 3 (PIV3) in Healthy Children

Inclusion Criteria: * Male or female aged 1 through 9 years old * In general good health * Seropositive for RSV (enzyme-linked immunosorbent assay \[ELISA\] titer \> 12 U/ml) and PIV3 (hemagglutination-inhibition \[HAI\] titer \> 1:8) * Subject's parent/legal representative available by telephone * Written informed consent and Health Insurance Portability and Accountability Act (HIPAA) authorization (if applicable) obtained from the subject's parent/legal representative * Ability of the subject's parent/legal representative to understand and comply with the requirements of the protocol as judged by the investigator * Ability to complete the follow-up period of 6 months following dosing as required by the protocol Exclusion Criteria: * Any fever and/or respiratory illness (e.g., cough or sore throat) within 7 days prior to randomization * Any drug therapy (chronic or other) within 7 days prior to randomization or expected receipt of such therapy through the protocol-specified blood collection 28-35 days after study vaccine dosing * Any current or expected receipt of systemic immunosuppressive agents including steroids; children in this category should not receive study vaccine until immunosuppressive agents including corticosteroid therapy have been discontinued for less than or equal to 30 days * Receipt of blood transfusion within 7 months prior to randomization or expected receipt through 35 days after study vaccine dosing * Receipt of immunoglobulin products within 11 m…