Mass drug administration trials of azithromycin: an analysis to inform future research and guidelines.

Background: In 2020, the World Health Organization published a guideline on the use of mass drug administration (MDA) of the broad-spectrum antibiotic azithromycin to reduce childhood mortality. As MDA-azithromycin to reduce mortality is considered for expansion to more settings and populations, care must be taken to maximize benefits and reduce risks (e.g., antimicrobial resistance or AMR) of this intervention. Completed and ongoing MDA-azithromycin cluster-randomized clinical trials can provide evidence on the extent to which these benefits and risks accrue and identify practices to monitor these effects and address evidence gaps in future trials.

Methods: We examined azithromycin clinical trials registered on ClinicalTrials.gov and the WHO International Clinical Trials Registry Platform from registry inception to December 31, 2023. We included trials for which azithromycin was administered for the prevention or treatment of a disease or condition that was not explicitly diagnosed or necessary for participant inclusion, and for which treatment was randomized by geographic units. We identified evidence, knowledge gaps, and trends and highlights across five domains: (1) targeting of MDA-azithromycin, (2) clinical endpoints, (3) co- and competing interventions, (4) spillover effects, and (5) AMR monitoring.

Results: Of 1589 screened studies, 30 met all inclusion criteria. These trials were conducted in 13 countries, predominantly (26/30) in sub-Saharan Africa. Nearly a third (9/30) of the trials included mortality endpoints, but few (2/9) included cause-specific mortality endpoints. New evidence suggests the benefits of widening the target age group and the persistence of mortality benefits in settings with competing interventions. Published practices to ensure geographic separation of communities in different treatment arms to reduce spillover effects were not customary. We found information on AMR monitoring practices for just over half the trials (16/30). Of these, half (8/16) included both phenotypic and genotypic AMR testing, and more than half collected specimens to assess the nasopharyngeal and gut microbiomes (9/16) and tested for non-macrolide resistance (11/16).

Conclusions: Further long-term MDA-azithromycin studies to determine which additional countries could benefit, interventions to accompany or replace this intervention, and the extent to which AMR spillover occurs may prove valuable as guidelines are revised.