To more accurately show how grueling it was for his character to survive, Vincent Price insisted on lifting real people into the back of his car instead of dummies. This is why it seems he's taking extra care with the bodies. For the scene at the pit, however, he's handling dummies for obvious reasons.
Although this is much more faithful to the book than The Omega Man (1971) and I Am Legend (2007) which are based on the same novel, it changes the main character's name from Robert Neville to Robert Morgan, while the other two leave it unchanged.
This film was originally going to be produced by Hammer Films of Great Britain. They decided not to make it and passed the script over to their U.S. associate, Robert L. Lippert, who produced the film in Italy.
Charlton Heston viewed this film before proceeding with his remake The Omega Man (1971). He described this version as "incredibly botched, totally unfrightening, ill-acted, sloppily written and photographed."