It is uncertain whether vitamin D can reduce respiratory infection.
To determine whether vitamin D supplementation reduces influenza and other upper viral respiratory tract infections.
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.