Coronavirus restrictions are starting to loosen and our cities and towns are showing more signs of life than they have in months. But health authorities and the federal and state governments insist that without an effective vaccine or treatment for coronavirus, life cannot fully return to normal. Australian scientists are at the forefront of this hunt for a vaccine, working around the clock on several promising contenders. The stakes are high, and the degree of difficulty is intense. On Monday Four Corners takes you into their world, where they face extraordinary scientific hurdles as well as extreme moral and ethical dilemmas.