If you’ve ever suffered after coming into contact with poison ivy you know how miserable it can be. Now Scientific American (SA) reports that U.S.-based scientists are reportedly working on a vaccine to combat humans’ responses to poison ivy, oak and sumac. They say the compound, called PDC-APB, will likely have to be injected once every year or two to prevent the poison plants’ effects. SA reports that Hapten Sciences, the company that licensed the compound, passed initial safety testing in human beings, and it’s about to be evaluated in a clinical trial. The American Skin Association says that as many as 50 million Americans are impacted by poison ivy, oak, or sumac every year, and about 85 percent of the population is allergic to the plants, while around 10 to 15 percent are extremely allergic. Also, the plants grow everywhere in the U.S. with the exception of Hawaii, Alaska, and some Nevada deserts. The CDC notes that recognition of the plants is an important step to avoiding them, as is washing garden tools and gloves, wearing long sleeves and long pants, washing pets and washing skin in soap and cool water as soon as possible if in contact with a poisonous plant.