Effect of High-Dose vs Standard-Dose Wintertime Vitamin D Supplementation on Viral Upper Respiratory Tract Infections in Young Healthy Children
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Clinical Question
Does high-dose vs standard-dose vitamin D supplementation reduce the incidence of viral upper respiratory tract infections in young children during the winter?
Bottom Line
Daily administration of high-dose compared to standard-dose vitamin D does not reduce URIs in young children in the wintertime.
Major Points
Prior studies suggested a link between low vitamin D levels and frequency of viral URIs. This study specifically looked at the incidence of viral URIs in young children during the wintertime and no association between dose of vitamin D and URI frequency (primary outcome) was found, nor in the secondary outcomes of median time to first laboratory-confirmed infection, number of parent-reported URIs between groups despite a significant difference in the serum values of vitamin D between the two groups at the end of the study.
Guidelines
Design
- Multisite, double-blind, randomized, parallel group
- N=703
- High-dose (n=354)
- Standard-dose (n=349)
- Setting: Toronto, Ontario, Canada (latitude 43 north)
- Enrollment: Winter seasons of 2011 to 2015; a child could only be randomized in to the trial during one winter season
- Mean follow-up: 6.2 months
- Analysis: Intention-to-treat
- Primary outcome: number of laboratory-confirmed viral upper respiratory tract infections based on on parent-collected nasal swabs over winter months
- Secondary outcomes: number of influenza infections, noninfluenza infections, parent-reported URIs, time to first URI, and serum vitamin D levels at study termination
Population
Inclusion Criteria
- Children who had well child checkups between September through November at a primary care research network of 8 pediatric or family medicine group practices participating in TARGet Kids! in Toronto
- Healthy children aged 1 to 5 years
Exclusion Criteria
- Gestational age younger than 32 weeks
- Chronic illness (other than asthma)
Baseline Characteristics
- Standard-dose group
- Girls: 39%
- Mean age: 2.8 years
- Mean 25-hydroxyvitamin D level: 36.9
- Average minutes in unstructured free play outdoors per week: 60
- Mean weight: 14.7kg
- High-dose group
- Girls: 45%
- Mean age: 1.5 years
- Mean 25-hydroxyvitamin D level: 35.9
- Average minutes in unstructured free play outdoors per week: 35
- Mean weight: 13.9kg
Interventions
- Radomized to standard-dose (400 IU/day) or high-dose (2000 IU/day)
- Parents were instructed to administer 1 drop of the solution (Kids Ddrops containing Vitamin D3) daily into their child's mouth
- Baseline vitamin D levels were drawn
- Over the counter vitamin D medicines were prohibited
- Parents completed a symptom checklist during the winter months
- Parents collected viral nasal swabs for every URI, with monthly phone calls for reminding
- Parents were not required to visit the physician to report the URI
- Between April and May the following year (4-8 months after randomization) a follow-up data collection and vitamin D level was completed in the office
Outcomes
Comparisons are intensive therapy vs. standard therapy.
Primary Outcomes
- Primary outcome
- ##% vs. ##% (HR ##; 95% CI ##-##; P=##)