Participant flow. Cohort A received V1 between 9 and 12 months after HCT. Cohort B received V1 between 13 and 24 months after HCT. Participants who did not return symptom diaries were monitored at the subsequent clinician visit for unsolicited AEs and SAEs. ¹Three of 3 participants with missing diaries had follow-up visits with no SAE. One patient died secondary to infection not related to trial intervention. ²Six of 7 participants with missing diaries had follow-up visits with no SAE or death. ³Six of 7 participants who did not have follow-up after V2 returned diaries and were monitored for SAEs at 30 days. Lack of follow-up was attributed primarily to COVID-related delays. ⁴Sixteen participants had ≤6-month follow-up after V1. IS, immunosuppression.