Background. Acute respiratory infection (ARI) is a major cause of morbidity and mortality in children, particularly under 5 years old, in developing countries. Bronchiolitis and pneumonia are the most common cause of death.Zinc has a major role in the human immune system, both  in non-specific and specific immunities, cellular and humoral immunity.Administration of zinc as prophylacticmay decrease incidence, episode frequency, duration and average durationof ARI in children.
Objectives. To determine the role of prophylactic zinc for incidence, episode frequency, duration and average duration episodes of ARI in children under 5 years old.
Methods. A randomized controlled trial (RCT), double blind randomizedstudy was performed in 160 infants, from December 2016 to April 2017 in Dr. WahidinSudirohusodo Hospital. Makassar, South Sulawesi.  Subject wareclassified into two groups, zinc group and placebo group.In zinc group, subjects were given 10 mg/day zinc for 2 weeks then being followed up forsign and symptoms of ARI for four mounts. 
Results. One hundred and sixty infants participatedin the study and were divided into zinc group (79 subjects) and placebogroup(81 subjects). There was no statistically significant difference in incidence of ARI between both groups. (38.8% in zinc group) and(44.4% in placebo group), (p = 0.406). Therewas also no significant difference in frequencyepisodes of ARI between both groups (1.2 episodes inzinc group and  1.19 episodes in placebo group). While, average of durationofARI, in zinc and placebo group was statistically significant5,28 and 6,28 day,respectively.(p = 0.05). Administration of zinc was also significantly related to shorter durationofARI(less than 5 days) (63.3% in zinc group) and (38.9% in placebo group), (p = 0.04).
Conclusion. Zinc as prophylactic is significantly correlated duration and averageduration of ARI. On the other hand, no signification correlation is found between zinc prophylactic and incidence and frequency episode of ARI also frequency episodes.