Study design and population.
DISEASES
This study was a randomized, double-blind, placebo-controlled trial to investigate the change of airway microbiota after azithromycin exposure among healthy adults. We distributed research posters in communities and recruited all the healthy participants from the community setting. Inclusion criteria for the healthy volunteers were men and women aged over 18 years who had no history of smoking, no history of any underlying diseases, and no existing abnormal symptoms. Detailed inclusion and exclusion criteria are provided in supplementary information (Table S4). Based on the selection criteria, we recruited 48 healthy volunteers randomly assigned to either the azithromycin or the placebo group (1:1) using a computer-generated random number table. We administered 500 mg azithromycin or 500 mg starch tablets once daily for 3 days. The drugs were contained in an identical opaque white capsule and packed in sealed kraft paper bags. All healthy volunteers, investigators, and study research staff were masked to intervention allocation.