A randomized trial found lower illness in the intervention arm, but 20% of participants in the intervention arm did not use assigned sanitizer while 5% in control obtained sanitizer independently. Which analysis approach best preserves randomization and estimates effectiveness?

• A. Intention-to-treat analysis (analyze participants in the groups they were randomized to regardless of adherence) combined with a secondary per-protocol analysis
• B. Replace non-adherent participants with new volunteers mid-trial to restore equal adherence rates
• C. Per-protocol analysis only, excluding non-adherent participants entirely and ignoring randomization allocation
• D. Convert the randomized trial into a case-control study after the fact and compare exposures retrospectively

Answer: (A)