Acute malnutrition accounts for an immense disease burden and is implicated as a key, underlying cause of child mortality in low resource settings. Child wasting, defined as weight-for-length more than 2 standard deviations below international standards, is a leading indicator to measure the Sustainable Development Goal target to end malnutrition by 2030. Prevailing methods to measure wasting rely on cross-sectional surveys that are unable to measure onset, recovery, and persistence - key features of wasting epidemiology that could inform preventive interventions and disease burden estimates. Here, we show through an analysis of 18 longitudinal cohorts that child wasting is a highly dynamic process of incident onset and recovery, and that peak incidence is between birth and 3 months - far earlier than peak prevalence at 12-15 months. By age 24 months the proportion of children who had ever experienced a wasting episode (33%) was more than 5-fold higher than prevalence (6%), suggesting that the wasting burden is likely far higher than cross-sectional surveys suggest. Seasonally driven changes in population mean weight-for-length were large (>0.5 z in some cohorts) and were synchronous with rainfall across diverse settings, creating potential for seasonally targeted interventions. Our results motivate a new focus on extending preventive interventions for child wasting to pregnant and lactating mothers, and for preventive and therapeutic interventions to include children below age 6 months in addition to current targets of ages 6-59 months.

Globally 149 million children under five are estimated to be stunted (length more than 2 standard deviations below international growth standards). Stunting, a form of linear growth failure, increases risk of illness, impaired cognitive development, and mortality. Global stunting estimates rely on cross-sectional surveys, which cannot provide direct information about the timing of onset or persistence of growth failure- a key consideration for defining critical windows to deliver preventive interventions. We performed the largest pooled analysis of longitudinal studies in low- and middle-income countries to date (n=31 cohorts, 62,993 children, ages 0-24 months), allowing us to identify the typical age of linear growth failure onset and to investigate recurrent faltering in early life. The highest incidence of stunting onset occurred from birth to age 3 months. From 0 to 15 months, less than 5% of children per month reversed their stunting status, and among those who did, stunting relapse was common. Early timing and low reversal rates emphasize the importance of preventive intervention delivery within the prenatal and early postnatal phases coupled with continued delivery of postnatal interventions through the first 1000 days of life.

Child growth failure is associated with a higher risk of illness and mortality, which contributed to the United Nations Sustainable Development Goal 2.2 to end malnutrition by 2030. Current prenatal and postnatal interventions, such as nutritional supplementation, have been insufficient to eliminate growth failure in low resource settings -motivating a search for key age windows and population subgroups in which to focus future preventive efforts. Quantifying the effect of early growth failure on severe outcomes is important to assess burden and longer-term impacts on the child. Here we show through an analysis of 35 longitudinal cohorts (108,336 children) that maternal and child characteristics at birth accounted for the largest attributable differences in growth. Yet, postnatal growth failure was larger than differences at birth, and characteristics of the child's household environment were additional determinants of growth failure after age 6 months. Children who experienced early ponderal or linear growth failure were at much higher risk of persistent growth failure and were 2.0 to 4.8 times more likely to die by age 24 months. High attributable risk from prenatal causes, and severe consequences for children who experienced early growth failure, support a focus on pre-conception and pregnancy as key opportunities for new preventive interventions. Our results suggest that broad improvements in wellbeing will be necessary to eliminate growth failure in low resource settings, but that screening based on weight could help identify children at highest risk of death before age 24 months.

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BackgroundIt is estimated that vaccinating 50%-70% of school-aged children for influenza can produce population-wide indirect effects. We evaluated a city-wide school-located influenza vaccination (SLIV) intervention that aimed to increase influenza vaccination coverage. The intervention was implemented in �95 preschools and elementary schools in northern California from 2014 to 2018. Using a matched cohort design, we estimated intervention impacts on student influenza vaccination coverage, school absenteeism, and community-wide indirect effects on laboratory-confirmed influenza hospitalizations. Methods and findingsWe used a multivariate matching algorithm to identify a nearby comparison school district with pre-intervention characteristics similar to those of the intervention school district and matched schools in each district. To measure student influenza vaccination, we conducted cross-sectional surveys of student caregivers in 22 school pairs (2017 survey, N = 6,070; 2018 survey, N = 6,507). We estimated the incidence of laboratory-confirmed influenza hospitalization from 2011 to 2018 using surveillance data from school district zip codes. We analyzed student absenteeism data from 2011 to 2018 from each district (N = 42,487,816 student-days). To account for pre-intervention differences between districts, we estimated difference-in-differences (DID) in influenza hospitalization incidence and absenteeism rates using generalized linear and log-linear models with a population offset for incidence