For many thousands of years people have spent a great deal of their life outdoors, getting ample sun exposure.
Today, most people work indoors, drive with windows rolled up, and put on sunscreen every time there's a chance of prolonged or intense sun exposure.
The result is widespread Vitamin D deficiency.
Today it takes special effort to get Vitamin D and Vitamin D is absolutely essential for health, especially for boosting your immune system. Studies show it helps prevent cancer, effectively fights cancer if you already have it, and helps prevent the common cold -- and the flu.
Getting Vitamin D from sunlight and/or supplementation is infinitely safer (and probably more effective) than getting the "flu shot."
There's nothing controversial about this, but since no one can get rich off sunlight and Vitamin D, you're unlikely to hear the pharmaceutical industry or its government agents talk about it much.
Here are a series of videos from experts, from ABC News, and from Stanford University. Watch them, and them make sure you are getting enough Vitamin D: