RE:enrollment Not 100%
I'd say enrolment has officially begun after treatment ( 2 treatments 24 hrs apart)
if someone is signed up and they died before treatment , that wouldn't make sense.
if they had treatment and died at day 15, then that tells you they didn't survive 28 days ( so not at day 30 as that would ensure 100% success )
but it would be an easy question for IR to answer