<p><strong>BACKGROUND: </strong>Pneumonia is the leading cause of death in children under age of 5 years worldwide. The role of vitamin D in respiratory infections including pneumonia is unclear; therefore, we aimed to determine if children with lower respiratory tract infections had low serum 25-hydroxyvitamin D3 .</p>

<p><strong>METHODS: </strong>We performed a case-control study of children ages 3-60 months from the Guatemala City metropolitan area, hospitalized with community-acquired pneumonia between September and December 2012. Controls were selected from the well-baby/care immunization clinics serving the population from which cases emerged. We analyzed serum 25-hydroxyvitamin D3 levels and conducted parental interviews to assess subject age, sex, race, feeding type, vitamin D supplementation, frequency of sun exposure, and maternal education. Height and weight were ascertained from medical records. Complete information was available for 70 (83%) of 84 eligible cases and 68 (60%) of 113 eligible controls.</p>

<p><strong>RESULTS: </strong>The median (IQR) serum 25-hydroxyvitamin D3 concentration for cases was 23.2 ng/ml (14.4-29.9) compared to 27.5 ng/ml (21.4-32.3) in controls (P = 0.006). Multiple regression analysis using an a priori cut-point for vitamin D of &lt;20 ng/ml showed that children with lower respiratory tract infections were more likely to have low 25-hydroxyvitamin D3 levels than controls (adjusted odds ratio 2.4, 95% confidence interval 1.1-5.2, P = 0.02).</p>

<p><strong>CONCLUSIONS: </strong>Children with lower respiratory tract infections in Guatemala had low 25-hydroxyvitamin D3 levels. Pediatr Pulmonol. © 2016 Wiley Periodicals, Inc.</p>