Yes.  Vitamin D helps our immune systems stay balanced, especially during the cold and flu season.  There are Vitamin D receptors and activating enzymes on the surfaces of all White Blood Cells. The role that vitamin D plays in keeping the immune system healthy is very complex because the immune system has to be perfectly balanced. If there is too much stimulation, autoimmune diseases can set in. If there is not enough immune system activity, frequent infections can occur.  In 2009, the National Institute of Health warned that low vitamin D levels are associated with frequent colds and influenza.  And so it appears that vitamin D helps keep the immune system balanced much like a gymnast walking on a balance beam.  Since the NIH announcement, there have been many studies to determine the best regimen of vitamin D supplementation and to better understand this association.  In 2017, a large analyses of prospective clinical trials showed that taking vitamin D reduces the odds of developing a respiratory infection by approximately 42% in people with low baseline levels of 25-hydroxyvitamin D; below 25 ng/mL  Learn more: https://www.pharmacytimes.com/news/vitamin-d-helps-the-immune-system-during-cold-and-flu-season