Acute Respiratory Infections

Abstract

Acute respiratory infections (ARIs) are a major cause of morbidity and mortality worldwide. Therefore, any intervention that would help reduce the incidence, decrease the severity, or improve the clinical course of these infections would be a huge advance for the care of people around the world. Vitamin D supplements may be such an intervention for populations with a high prevalence of vitamin D de fi ciency. Unfortunately, examining ARI as an outcome measure is complex given its protean categorization. Nonetheless, multiple case-control studies have noted an association between children with rickets and increased incidence of ARI. Furthermore, prospective, observational studies have linked low levels of 25-hydroxyvitamin D (25(OH)D) with adverse impact on both the incidence and clinical course of ARI. More recently, randomized controlled trials have been conducted, but these trials have had mixed results for reducing ARI incidence. Despite the mixed RCT results, when all of the data about vitamin D and ARI are taken together, we believe that current evidence suggests that vitamin D supplementation of individuals with low vitamin D status decreases the incidence of ARI. Nevertheless, firm recommendations will require larger RCTs, with adequate dosing of vitamin D supplementation and enrollment of diverse populations that include both high-risk and non-high-risk groups. Furthermore, the scientific rigor and accuracy of these RCTs will evolve as we learn more about not only vitamin D dosing, metabolism, and genetics but also specific ARI viruses, viral-bacterial interactions, and the potential importance of the respiratory microbiome.and accuracy of these RCTs will evolve as we learn more about not only vitamin D dosing, metabolism, and genetics but also specific ARI viruses, viral-bacterial interactions, and the potential importance of the respiratory microbiome.