The ONLY thing that his idea has in common is that their plots both have a cure in them. In I Am Legend it is a cure for cancer. In his story, it is a cure for everything. In I Am Legend, the cure turns into a virus that causes everyone to turn into a zombie. In his story everyone remains cured and ends up living a lot longer. This increase in life expectancy makes for overpopulation. The 'cure' that kills in his story kills indirectly. As opposed to I Am Legend, where the cure is the direct cause of the death of civilisation.