Comparing a multi-dose drug to no drug exposure in a cohort study: Censoring events between doses I am interested in assessing the association between the two doses of a dietary supplement on an event of interest.
The primary exposure is 'two doses of the supplement', and the comparator is 'no exposure to this supplement'. I am planning on performing time-to-event analysis comparing the two exposure groups.
My question is: By excluding those individuals who experience the event of interest after just one dose of the supplement (i.e., they have not had the opportunity to receive the second), isn't there a survivorship bias that is introduced? If so, how could I account for this?

There's a lot of important factors that are unclear the question, but without understanding all the detail, it would sound like an Intention to Treat analysis would be the simplest way to address the issue.
This would mean you would compare the differences between those assigned to treatment and control, regardless if the full treatment was applied or not. This would essentially estimate the difference between the population assigned a treatment vs those who were not, so an estimate of what happens when the treatment is assigned rather than when the treatment is correctly taken.
