More from Prevention: 10 Worst Germ Hot Spots Because there is not yet a vaccine for RSV, and because flu vaccines aren’t 100% effective, researchers decided to investigate red ginseng extract, which had already been proven a worthy immune-enhancer (ginseng’s ability to successfully help ward off colds was shown in a 2006 study, and earlier research also suggests it has antiviral action against RSV and flu). In this new study, Sang-Moo Kang, PhD, a professor at the Institute for Biomedical Sciences at Georgia State in Atlanta, who specializes in developing vaccines that protect against bacterial and viral disease such as influenza and RSV, discovered that red ginseng extract protects the survival of human lung epithelial cells infected with Several species of ginseng and types of ginseng extracts exist, but to fight theflu, Kang recommends Korean red ginseng, which is a cured ginseng root extract. “Ginsenosides are active ingredients in Korean red ginseng that help the body deal with stress, disease, and fatigue,” says Kang. “These substances are have anti-inflammatory, antioxidant, and even anti-carcinogenic properties,” he adds. Progena Korean Red Ginseng passed consumerlab.com testing for potency and purity. Follow label directions for dose. More from Prevention: The Best Supplements For Women