Vitamin D (VD) protects mice from severe influenza infection. We examined how VD metabolism genes, Cyp27b1, Cyp24a1, and the vitamin D receptor (VDR), were affected by influenza infection. Results showed that Cyp27b1 and VDR mRNA in the lung were not different throughout infection. Conversely, Cyp24a1 mRNA expression was significantly increased (P<0.05) at day 6 post-infection, suggesting increased VD metabolism in the lung. This result supports the importance of VD in the host response to influenza.