Subjects will be randomized at a 1:1 ratio to receive a single injection of rAd5 or the DNA prime-rAd5 boost schedule and will be stratified by gender to achieve approximately equal distribution of each gender into the two vaccination schedules. Subjects randomized to Group 1 may receive the vaccination on enrollment day or schedule the day of vaccination to occur within 6 weeks followed by the expected 24 hours in the inpatient unit and day 3 post-vaccination sample collections for the frequent sampling that will immediately ensue according to the sample collection schedule. Subjects randomized to Group 2 will receive the first of three DNA vaccinations and schedule projected dates for the subsequent injections and timepoints with intensive sample collection schedules. Due to the need to commit to about 3 days of disruption in normal daily activities, starting with the day of rAd5 vaccination on either schedule, flexibility in scheduling of the rAd5 vaccination is included in the protocol plan.