While only 200 of the more than 3,000 snake species in the world are considered venomous enough to kill humans, most people would probably say they avoid all snakes at all costs. Tim Friede, a 37-year-old man from Wisconsin, is not one of these people.

Over the course of 16 years, Friede has allowed deadly snakes to bite him in hopes that doing so will one day lead to the creation of a vaccine for snake venom. He’s already experienced over 160 bites from a variety of snakes, including the black mamba, who can kill a human in 20 minutes with only two drops of venom; the inland taipan, whose venom kills in 45 minutes; and the cobra, which, depending on the type, can kill an elephant with a single bite.

Friede, an amateur scientist, is not undertaking this venture alone. He has the help of microbiologist Dr. Brian Hanley and his company Butterfly Sciences. Through their work together, Friede has nearly doubled the number of antibodies in his body capable of fighting venom. Hanley attributes this resistance to the years of snake bites and self-injections of venom Friede has received.

Although Friede has survived the effects of the toxins, he hasn’t walked away unharmed. Once, he injected himself with monocled cobra venom powerful enough to cause necrosis (tissue death) in his leg — he subsequently self-amputated the muscle. In 2011, only two bites from a cobra were enough to put him in a coma. Yet, despite the high level of risk, Friede is committed to his mission, saying, “I will not stop doing this until the vaccine is in the field, or I die.”