Azithromycin treatment effect on mortality among 1–11-month-old infants
IRD
We will tabulate the mortality (deaths/1000 PYR and absolute numbers) per arm and per 3-month intervals preceding the second to ninth visit. To investigate if azithromycin treatment reduces mortality among 1–11-month-old infants, we will estimate incidence rate ratio (IRR) and its 95% CI to compare the treatment regimens. We will use mixed-effects Poisson model to estimate intervention effects between treatment groups, with random intercepts for clusters (villages), using log link function with person-years as an offset variable. At maximum, an infant can receive the treatment at four MDAs, thus provide up to 1 year of follow-up time to the study data.The main analysis hypothesis testing will be conducted as one-sided, that is, we hypothesize there to be lower mortality in the treatment groups. The decision to use one-sided test was based on the existing evidence of AZI having a potentially beneficial effect on early childhood mortality in previous trials [In the main analyses, we will adjust for stratification factor in the randomization scheme (village size category) as a fixed effect. The main analysis will not make additional adjustments for covariates.The mixed-effects model with log link function for the primary aim on intervention effect on mortality will provide the IRR. To understand the population importance of the intervention, we will use non-linear combinations of the parameter estimates from the same mixed-effects model to obtain average estimates of incidence rate difference (IRD) [