A Cochrane review included 6 studies with a total of 5 193 children aged from two to 59 months. The studies were conducted in Bangladesh, India, Peru, and South Africa. Most included studies were from disadvantaged urban areas of low-income countries, and in two studies, either children or their mothers had HIV positive status. Analysis showed that zinc supplementation reduced the incidence of pneumonia (RR 0.87, 95% CI 0.81 to 0.94, 6 studies, n=5 193) and prevalence of pneumonia (RR 0.59, 95% CI 0.35 to 0.99, 1 study, n=609). It was found on subgroup analysis that zinc reduced the incidence of pneumonia defined by specific clinical criteria (i.e. confirmation by chest examination or chest radiograph; RR 0.79, 95% CI 0.0.71 to 0.88, 4 studies, n=3 261) but had no effect on lower specificity pneumonia case definition (i.e. age specific fast breathing with or without lower chest indrawing; RR 0.95, 95% CI 0.86 to 1.06, 4 studies, n=1 932).