Safety and Tolerability Study to Evaluate MEDI-534 in Children 6 to < 24 Months of Age

Inclusion Criteria: * Male or female whose age on the day of randomization is 6 to \<24 months (reached 6th month birthday and not yet reached 2nd year birthday) * Subject is seronegative to both RSV and PIV3 at screening * Subject was the product of normal full term pregnancy (defined as \>36 weeks gestation) * Subject is in general good health * Subject's legal representative is available by telephone * Written informed consent and 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, which will be through the end of RSV season (provisionally defined as 01/Apr for the United States) or 180 days after the final dose of study vaccine, whichever is later * 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 (equal to or greater than 100.4°F \[equal to or greater than 38.0°C\], regardless of route) or lower respiratory illness (Section 4.1.2) within 7 days prior to randomization * Moderate or severe nasal congestion that in the investigator's opinion could prevent intranasal delivery of vaccine * Any drug therapy (chronic or other) within 7 days prior to randomization or expected receipt through the protocol-specif…