Rabies is among the most terrifying viruses to get. According to the Centers for Disease Control, “once clinical signs of rabies appear, the disease is nearly always fatal.” (Really: there have been fewer than 10 documented cases of survival once symptoms appear.) Luckily for us—and our pets—Louis Pasteur developed a vaccine that can stop things from getting to that point. The first time the vaccine was ever administered to a human being–on this day in 1885–was by Pasteur himself.