A Study to Evaluate the Safety, Tolerability, Immunogenicity and Vaccine-like Viral Shedding of MEDI-534, Against Respiratory Syncytial Virus (RSV) and Parainfluenza Virus Type 3 (PIV3), in Healthy 6 to <24 Month-old Children and in 2 Month-old Infants

Inclusion Criteria: * Male or female whose age on the day of randomization falls within one of the two age groups: 6 to less than (\<) 24 months (more than \[\>\] 6 months of age and not yet reached their 2nd year birthday), Cohorts 1 and 2 2 months (+/- 4 weeks), Cohorts 3, 4, and 5 * Cohorts 1 and 2 only: Subject is seronegative to both Respiratory Syncytial Virus (RSV) and human Parainfluenza Virus Type 3 (hPIV3) at Screening * Subject whose gestational age was greater than or equal to (\>=) 36 weeks * Subject is in general good health with normal growth (that is, body weight greater than (\>) third percentile per world health organization \[WHO\] simplified weight-per-age field tables * Subject's legal representative is available by telephone * Written informed consent and Health Insurance Portability and Accountability Act (HIPAA) authorization (if applicable) obtained from the subject's legal representative * Subject's legal representative is able to understand and comply with the requirements of the protocol as judged by the investigator * Subject is available to complete the follow-up period 1-year after receipt of the first dose of study vaccine * Subject's legal representative must be willing and able to bring the subject to the study site for evaluation of respiratory illness in accordance with the protocol. Exclusion Criteria: * Any fever (\>=100.4 degrees Fahrenheit \[\>=38.0 degrees Celsius\], regardless of route) or lower respiratory illness within 7 days…