Effect of Vitamin D supplementation to reduce respiratory infections in children and adolescents in Vietnam: A randomized controlled trial

Influenza Other Respir Viruses. 2019 Mar;13(2):176-183. doi: 10.1111/irv.12615. Epub 2019 Jan 4.


Background: It is uncertain whether vitamin D can reduce respiratory infection.

Objective: To determine whether vitamin D supplementation reduces influenza and other upper viral respiratory tract infections.

Methods: A total of 1300 healthy children and adolescents between the ages of 3 and 17 years were randomized to vitamin D (14 000 U weekly) or placebo for 8 months in Vietnam. The primary outcome was reverse transcriptase (RT)-PCR-confirmed influenza infection, and the coprimary outcome was multiplex PCR-confirmed non-influenza respiratory viruses. Participants, caregivers, and those assessing outcomes were blinded to group assignment.

Results: A total of 650 children and adolescents were randomly assigned to vitamin D and 650 to placebo. The mean baseline serum 25-hydroxyvitamin D levels were 65.7 nmol/L and 65.2 nmol/L in the intervention and placebo groups, respectively, with an increase to 91.8 nmol/L in the vitamin D group and no increase, 64.5 nmol/L, in the placebo group. All 1300 participants randomized contributed to the analysis. We observed RT-PCR-confirmed influenza A or B occurred in 50 children (7.7%) in the vitamin D group and in 43 (6.6%) in the placebo group (hazard ratio [HR]: 1.18, 95% CI: 0.79-1.78). RT-PCR-confirmed non-influenza respiratory virus infection occurred in 146 (22.5%) in the vitamin D group and in 185 (28.5%) in the placebo group (hazard ratio [HR]: 0.76, 95% CI: 0.61-0.94). When considering all respiratory viruses, including influenza, the effect of vitamin D in reducing infection was significant, HR: 0.81, 95% CI: 0.66-0.99.

Conclusion: Vitamin D supplementation did not reduce the incidence of influenza but moderately reduced non-influenza respiratory viral infection.

Keywords: influenza; randomized trial; respiratory viruses; vitamin D.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Child
  • Child, Preschool
  • Clinical Laboratory Techniques
  • Dietary Supplements*
  • Double-Blind Method
  • Female
  • Humans
  • Incidence
  • Influenza, Human / diagnosis
  • Influenza, Human / prevention & control*
  • Male
  • Orthomyxoviridae / genetics
  • Respiratory Tract Infections / prevention & control*
  • Respiratory Tract Infections / virology
  • Vietnam
  • Vitamin D / administration & dosage*
  • Vitamins / administration & dosage*


  • Vitamins
  • Vitamin D