Night of the Comet (1984)

Two sisters, high school seniors in the early 1980s, awaken one morning to blood red skies and the realization that the human race has been wiped out. This becomes apparent that anyone who was not surrounded by steel when Earth recently passed through the tail of a comet has been reduced to a pile of red dust (the trace elements of human chemical makeup). They encounter a friendly truck driver and take over the airwaves at a local radio station in an attempt to get help. Unfortunately, they attract the attention of a group of scientists who knew what the effects of the comet would be. They hide underground in a steel laboratory, but carelessly left the vents open. Now as various survivors of the comet who were only partially surrounded by steel are decaying into flesh-hungry zombies, the scientists are attempting to come up with a vaccine made of the blood of people who were not infected by the comet. Thus the trio must fight their way past not only roving packs of the cannibal zombies, but also outsmart a pack of scientists desperate not to become that way themselves.