The Effect of Mass Azithromycin Distribution on Childhood Mortality: Beliefs and Estimates of Efficacy

Abstract

A cluster-randomized trial demonstrated that mass oral azithromycin distribution reduced childhood mortality 49.6% (Trachoma Amelioration in Northern Amhara [TANA]). The relative risk of childhood mortality was then estimated using two approaches: an expert survey and a Bayesian analysis. The survey asked public health experts to estimate the true effect of mass azithromycin distribution on childhood mortality. The Bayesian estimation used the TANA study's results and prior estimates of the efficacy of other effective population-level interventions. The experts believed mass azithromycin reduces childhood mortality (relative risk = 0.83, 95% credible intervals [CrI] = 0.70-1.00). The Bayesian analysis estimated a relative risk of 0.71 (95% CrI = 0.39-0.93). Both estimates suggest that azithromycin may have a true mortality benefit, though of a smaller magnitude than found in the single available trial. Prior information about nonantibiotic, population-level interventions may have informed the expert's opinions. Additional trials are needed to confirm a mortality benefit from mass azithromycin.

Figure 1.

Comparison of estimates of the relative risk of childhood mortality. In A–D, the x-axis represents the relative risk of childhood mortality. The y-axis is a unit-less density measure. A depicts the survey distribution, a probability density function created by pooling 28 skew-normal distributions fit to the questionnaire responses. The pooled function (light gray, dashed outline) is shown along with scaled-down representations of individual responses (darker gray, grey outline). B shows the Bayesian empirical prior distribution, which was calculated from meta-analysis of Cochrane reviews. The pooled function (dark gray, black outline) is shown along with scaled-down representations of the seven interventions (gray, gray outline). C shows the Bayesian analysis, which contains the empirical distribution as the prior probability (dark gray, black outline), the results of the Trachoma Amelioration in northern Amhara (TANA) study as the likelihood (light gray, dashed outline), and the resulting posterior probability (gray, dashed outline). D compares the survey distribution (light gray, dashed outline) to the Bayesian posterior (gray, dashed outline).