Last winter we were fortunate that the H1N1 virus did not claim as many lives as it might have claimed had it blossomed into a pandemic such as the 1918-19 flu virus.  Back in 1918-19 the H1N1 flu virus killed at least 50 million worldwide.  What needs to be noted is the sequence of the assaults on the human population in those two flu seasons.  During the first year not many people died of the virus, but the next year it returned with a vengeance and killed most of the folks included in the 50 million deaths due to the flu.  The second round was deadlier, because it had mutated.  Similarly last year saw fewer deaths due to the H1N1 flu virus than had been expected, so this winter if the H1N1 flu virus returns it may mutate and result in the large number of  deaths that occur when a flu pandemic strikes.  Fortunately there is good news for seniors who want to take preemptive aging steps to protect their senior health against winter flu viruses such as the H1N1 virus by building up their immune system.  Numerous studies have shown that a deficiency of vitamin D is linked to influenza infections. The Harvard Medical School, that normally recommends getting vitamins through food, makes an exception for supplementing with vitamin D. The good news is that the vitamin D supplements that duplicate the form D3 made by our bodies in sunlight are very inexpensive. The D3 form that is more readily absorbed by our bodies is preferred over the less potent form D2. Together with eating a healthy diet and getting enough sleep, supplementing with vitamin D3 will support a layered defense against infection by the H1N1 flu.