Eligibility

MORDOR (Macrolides Oraux pour Réduire les Décès avec un Oeil sur la Résistance) was a cluster-randomized trial conducted in the Malawian district of Mangochi, in the Nigerien districts of Boboye and Loga, and in the Tanzanian districts of Kilosa and Gairo, with communities as the unit of randomization. The community that served as the randomization unit was a health surveillance assistance area in Malawi, a grappe (i.e., a cluster of households representing the smallest government health unit) in Niger, and a hamlet in Tanzania. None of the districts were eligible for mass distributions of azithromycin for trachoma on the basis of the most recent mapping, and none of the children who participated in the trial had previously received azithromycin. Enrollment was based on census information available before the trial. Communities with a population between 200 and 2000 inhabitants on the most recent census were eligible for enrollment (see the Supplementary Appendix, available with the full text of this article at NEJM.org). Communities remained in the trial even if the population drifted out of this range. All children 1 to 59 months of age (truncated to month) who weighed at least 3800 g were eligible to receive azithromycin or placebo.

Randomization and Masking

Lists of communities from the most recent pretrial census were submitted to the data coordinating center at the University of California, San Francisco (UCSF). For each country, communities were randomly assigned in equal proportions to 1 of 10 letters, with 5 letters coded for azithromycin and 5 for placebo (more information is provided in the statistical analysis plan in the protocol, available at NEJM.org). Randomization was performed with the sample function in R software, version 3.1 (R Foundation for Statistical Computing). Only key trial personnel were aware of which letters corresponded to each group. Participants, observers, investigators, and data-cleaning team members were unaware of the group assignments. Centralized randomization and simultaneous assignment of communities facilitated complete concealment of the assignments. The placebo contained the vehicle of the oral azithromycin suspension and was bottled and labeled identically to azithromycin. Both placebo and azithromycin were donated by Pfizer, which reviewed the protocol but had no other role in the trial.

Census

A house-to-house census was performed during five prescribed 6-month periods, with allowance for a 2-month grace period for the initial census. At the initial census, all households in the community were recorded in a custom-built mobile application (Conexus); the name of the head of household and the global positioning system coordinates were used to facilitate location of the household for the following census. All children 1 to 59 months of age in the household were identified. Pregnant women and children younger than 1 month of age were also documented in anticipation of the next census. At follow-up censuses, the vital status (alive, dead, or unknown) and residence (living in community, moved outside community, or unknown) were recorded for the children who had been present in the previous census records. Pregnant women and children younger than 1 month of age were documented, and children 1 to 59 months of age who had moved into the community after the previous census were also documented and were offered participation. Census data were collected in communities in the same general order throughout the trial. Data were uploaded to the Salesforce cloud database service (Salesforce). Data cleaning was performed with the use of the Salesforce platform; Stata software, version 13.1 (Statacorp); and R software.

Intervention

Each child 1 to 59 months of age at the time of the census was offered a single directly observed dose of oral azithromycin or placebo (according to the randomization of their community). Children were given a volume of suspension corresponding to at least 20 mg per kilogram of body weight, calculated with the use of a height stick (see the protocol), in accordance with the country’s trachoma program guidelines, or by weight for children unable to stand. Children who were known to be allergic to macrolides were not given azithromycin or placebo. Azithromycin or placebo was administered at the time of the census or during additional visits in an attempt to achieve at least 80% coverage. Administration of trial medication or placebo was documented in the mobile application for each child, and community coverage was calculated relative to the census. The parents or guardians of the children and the local health posts were instructed to contact a village representative regarding any adverse events noted within 7 days after administration of azithromycin or placebo; the village representative reported the events to the site coordinator, who in turn reported the events to UCSF.

Primary Outcome

The prespecified primary outcome was the community-level, aggregate, three-country mortality rate determined with the use of data from twice-yearly censuses. Each intercensal period was analyzed separately, with a death counted only when a child was recorded as having been alive and living in the household at the time of one census and recorded as having died while residing in the community by the time of the next census. By design, no attempt was made to track down a child’s status after the child moved out of the community. Person-time at risk was measured as the days between consecutive censuses; children who moved, died, or had an unknown follow-up status contributed to one half of the intercensal period. All children documented as being alive and residing in the household at the time of the initial census of each intercensal period were included in the analysis. No changes to trial outcomes were made after the trial had begun.

Subgroup Analyses

Mortality rates were assessed according to country site and age group. An abbreviated version of the 2007 World Health Organization (WHO) verbal autopsy questionnaire for children 4 weeks to 14 years of age was used to collect data for verbal autopsies.19 Causes of death were assigned according to an algorithm based on a published verbal autopsy hierarchy.20

Trial Oversight

Approval for the trial was obtained from the ethics committees at the College of Medicine, University of Malawi, Blantyre; the Niger Ministry of Health; the Tanzanian National Institute for Medical Research; the London School of Hygiene and Tropical Medicine; the UCSF Committee on Human Research; Emory University; and Johns Hopkins University School of Medicine. Oral informed consent was obtained in Malawi and Niger, and written informed consent was obtained in Tanzania. The trial was conducted in accordance with the principles of the Declaration of Helsinki. No incentives were offered for participation. All children in the communities in Niger were offered treatment with azithromycin at the conclusion of the trial. By design, communities in Malawi were entered into the country’s trachoma-control program, even though prior district-level data had not met the criteria for mass distribution.

A data and safety monitoring committee provided oversight. The members of the steering committee (see the Supplementary Appendix), who were also investigators in the trial, designed the trial and vouch for the accuracy and completeness of the data and for the fidelity of the trial to the protocol. Full details of the trial design and analyses are provided in the protocol and the statistical analysis plan. The last author wrote the initial draft of the manuscript. All the authors contributed to subsequent revisions and agreed to submit the manuscript for publication.

Statistical Analysis

We estimated that the inclusion of 620 communities per country would provide at least 80% power to detect 10% lower all-cause mortality overall with azithromycin than with placebo. Specifically, we assumed that mortality rates would be between 14 and 20 deaths per 1000 person-years in the placebo group, that the average community sizes would be 600 to 799 people (of whom 16.7 to 19.0% would be children 1 to 59 months of age), that coefficients of variation would be between 0.40 and 0.51, and that the loss to follow-up would be 10%.

The prespecified primary analysis was negative binomial regression of the number of deaths per community, with treatment group and country as predictors and total person-time at risk as an offset. All three country sites contributed to the primary outcome. Hypothesis testing was two-sided, with an overall alpha level of 0.05 for the interim and final analyses. P values were determined with Monte Carlo permutation testing (10,000 replications). An interim efficacy analysis after the 12-month census was designed to spend 0.001 of the overall alpha level, with an alpha level of 0.049 reserved for the primary 24-month analysis. Community-level clustering was taken into account by the dispersion parameter in the negative binomial regression model. Prespecified subgroup analyses included negative binomial regression of community-level mortality rates according to country, age group, and intercensal period (details are provided in the statistical analysis plan in the protocol). A sample of 250 verbal autopsies were randomly selected from each country site and were compared with the use of the chi-square statistic, with clustering taken into account by community-level permutation. All statistical analyses were conducted with R software.