Participants
272 participants were enrolled in the study (269 for RCT analysis, 3 for piloting procedures). Overall, 91 participants were randomized to the live call arm, 91 were randomized to the technology-delivered booster arm, and 90 were randomized to the SOC wait-list control arm. Within the technology-delivered booster arm, 31 chose booster delivery by SMS and 60 chose booster by IVR. Among the 90 people randomized to the wait list, when offered the intervention, 69 chose live call delivered booster calls, 10 chose technology-delivered booster calls (9 SMS and 1 IVR), 6 declined any intervention, and 5 were lost to follow up. In total, 160 received the intervention with the live call boosters, and 101 received the intervention with automated technology boosters (40 SMS and 61 IVR).