= Solution
Measure receipt and transfers directly rather than inferring them only from the outcome difference. Use identifiable pack codes and confidential early follow-up to record whether packs were retained, lost, taken, given away or administered, and to whom. Where feasible, corroborate administration reports with care records and establish whether recipients belonged to the opposite randomized group.
A process-evaluation sample across both arms can estimate the frequency and direction of <treatment contamination>. Separate receipt tracking from blinded outcome ascertainment where possible. Keep randomized assignments for the primary <intention-to-treat analysis>: excluding transfers or reclassifying participants by receipt can introduce <confounding>, since receipt behavior is not randomized. Receipt data can inform a supplementary analysis whose additional assumptions are explicit.
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