A study by Ovsyannikova et al. enrolled 745 healthy school children who had documentation of having two doses of measles, mumps, and rubella (MMR) vaccines and found that specific allelic variants in the vitamin D receptor (VDR) and retinoid X receptor alpha (RXRA) encoding gene were associated with higher measles-virus induced cytokine response.[12] However, the vitamin D levels were not assessed in the study. The gene discussed is VDR; the disease is measles.