Pamela Sargent 
Sudden Star 

The appearance of a white star bathing the world in a deadly glare turns Earth into a nightmare of fear and death. Rape and murder are as common as suicide. Medical help is allowed only for certain diseases, and only the most resourceful and corrupt survive. Dr. Simon Negron dares to defy the medical code by giving insulin to a diabetic. His crime makes him a fugitive with only a young prostitute as an ally, a haunted man running for his life in a nightmare world of increasing madness. Published in the UK under the title The White Death.