Table 8  Efficacy of zinc in treating respiratory illnesses in childhood.
Study  Author  Country  Study Population  Dosage  Results
Randomized, double-blind, placebo-controlled clinical trial of the efficacy of treatment with zinc or vitamin a in infants and young children with severe acute lower respiratory infection.  Mahalanabis et al., 2004 [253]  India  153 children hospitalized with severe ALRI  10 mg twice daily for 5 days  Significantly reduced duration of fever and very ill status in boys, but not in girls.
Efficacy of zinc in the treatment of severe pneumonia in hospitalized children <2 y old.  Bose et al., 2006 [254]  India  299 children hospitalized with severe pneumonia  20 mg/day during hospital stay  No overall effect on the duration of hospitalization or of clinical signs associated with severe infection.
A randomized controlled trial of the effect of zinc as adjuvant therapy in children 2–35 months of age with severe or nonsevere pneumonia in Bhaktapur, Nepal.  Valentiner-Branth et al., 2010 [255]  Nepal  Over 2000 children with pneumonia  10 mg if aged 2–11 months, 20 mg if aged > or =12 months, for 14 days  No decrease in risk of treatment failure nor accelerated recovery.
A randomized controlled trial of oral zinc in acute pneumonia in children aged between 2 months and 5 years.  Ganguly et al., 2011 [256]  India  98 children with pneumonia  10 mg/day if <1 year, 20 mg if >1 year of age  No improvement in symptom duration.
The efficacy of zinc supplementation on outcome of children with severe pneumonia. A randomized double-blind placebo-controlled clinical trial.  Valavi et al., 2011[257]  Iran  128 children with severe pneumonia  2 mg/kg/day, max 20 mg, for 5 days  Shorter time for symptoms resolution and shorter hospital stay.
Zinc Supplementation in Severe Acute Lower Respiratory Tract Infection in Children: A Triple-Blind Randomized Placebo Controlled Trial.  Bansal et al., 2011 [258]  India  Children hospitalized with ALRI  20 mg/day for 5 days  No decrease in recovery time or in duration of hospital stay.
Role of zinc in severe pneumonia: a randomized double bind placebo-controlled study.  Shah et al., 2012 [259]  Nepal  Children hospitalized for severe pneumonia  20 mg/die for 7 days  No effect on clinical recovery from severe pneumonia.
A randomized controlled trial of zinc as adjuvant therapy for severe pneumonia in young children.  Basnet et al., 2012 [260]  Nepal  610 children with severe pneumonia  10 mg if <11 months, 20 mg/day if >11 months, for 14 days  Slightly faster recovery, slightly lower risk of treatment failure but not statistically significant.
Zinc adjunct therapy reduces case fatality in severe childhood pneumonia: a randomized double-blind placebo-controlled trial.  Srinivasan et al., 2012 [261]  Uganda  352 children with severe pneumonia  20 mg if ≥12 months, 10 mg if <12 months, for 7 days  No significant effect on time to resolution of symptoms; decreased mortality rate.
Efficacy of zinc given as an adjunct in the treatment of severe and very severe pneumonia in hospitalized children 2–24 months of age: a randomized, double-blind, placebo-controlled trial.  Wadhwa et al., 2013 [262]  India  550 children hospitalized with severe pneumonia  20 mg/day during hospital stay  No difference in time to recovery.
Zinc as an adjunct to the treatment of severe pneumonia in Ecuadorian children: a randomized controlled trial.  Sempertegui et al., 2014 [263]  Ecuador  450 children hospitalized with pneumonia  20 mg/day during hospital stay  No effect on time to pneumonia resolution nor in treatment failure rate.Higher basal zinc concentrations associated with faster resolution of chest indrawings.
Effect of zinc supplementation on infants with severe pneumonia.  Yuan et al., 2016 [264]  China  73 infants hospitalized for pneumonia  10 mg/day if <6 mo; 20 mg/day if >6 moduring hospital stay  No improvements on clinical outcomes.
Zinc as an adjunct therapy in the management of severe pneumonia among Gambian children: randomized controlled trial.  Howie et al., 2018 [265]  Gambia  Over 600 children with severe pneumonia  10 mg if <12 mo; 20 mg if > 20 mo, for 7 days  No benefit in treatment failure rates or time to recovery from respiratory symptoms; marginal benefit in rapidity of resolution of chest indrawings.
Zinc supplementation promotes a th1 response and improves clinical symptoms in fewer hours in children with pneumonia younger than 5 years old. A randomized controlled clinical trial.  Acevedo-Murillo et al., 2019 [266]  Mexico  103 children hospitalized for pneumonia  10 mg/day if <1 year; 20 mg/day if >1 year during hospital stay  Quicker improvement in clinical status, oxygen saturation and respiratory rate. Patients’ baseline zinc levels were below normal range.
A randomized controlled trial of zinc supplementation in the treatment of acute respiratory tract infection in Thai children.  Rerksuppaphol et al., 2019 [267]  Thailand  64 hospitalized children with ALRI  30 mg/day during hospital stay  Faster symptoms resolution and shorter hospital stay.
ALRI, acute lower respiratory tract infection.