With many reporting a shortage on flu vaccines some have wondered about a more natural preventive method? Dr. Blair Masters with Arkansas Physical Health And Rehab says one great option is vitamin d, "The great thing about vitamin d is it actually helps after you get the virus too . It boost the immune system. Makes your immune system work harder. Its very effective before as a preventative. Everyone needs it everyday and its also good to help your body get rid of the flu once you get it" Dr. Masters says The Mayo Clinic recommends five-thousand international units or IU's a day if you're healthy and to up the amount if you are sick. But as always, check with your Doctor.