Randomization and masking
Following baseline questionnaires and blood draw, we randomized participants to: (1) in-person brief workbook-based alcohol counseling at two regularly-scheduled quarterly clinic visits plus interim boosters delivered every 3 weeks by phone (live call arm); (2) in-person brief workbook-based alcohol counseling at two regularly-scheduled quarterly clinic visits plus twice-weekly boosters delivered via two-way automated calls either by SMS or IVR (technology arm); or (3) standard of care which included brief advice, with a wait-listed intervention (control arm). We created a computer-generated randomization list with a 1:1:1 ratio using blocks of nine for pre-printing on scratch cards that the participants scratched with a coin to reveal the randomization arm to themselves and the study staff. There was no masking of study arm. Those randomized to the intervention arms were referred to the study counselor for in-person counseling and training on the booster calls. Those randomized to the control arm had no contact with the study counselors during the first nine months of the study, but were offered the study intervention after their nine-month study visit.