It would be a mistake to think that SHOCK! programming introduced the horror film host to television. Maila Nurmi, as Vampira, set the template with THE VAMPIRA SHOW that premiered in Los Angeles on May 1, 1954 on KABC. Films like REVENGE OF THE ZOMBIES and FOG ISLAND were exhibited, with Vampira talking to the TV audience and doing commentary on the films. The show began at the midnight slot (another influence for many SHOCK! programs), with adjustments to 11pm then 10:30pm. The character of Vampira became a celebrity in the LA area, and even beyond, with a LIFE magazine spread and an appearance on a THE RED SKELTON SHOW that also hosted Bela Lugosi, Peter Lorre and Lon Chaney, Jr.
One can only speculate that Screen Gems, in creating the SHOCK! catalog and offering up the suggestion of a horror host for the films therein, had been aware of Vampira, and planned accordingly.
Horror hosting on television arrived even before THE VAMPIRA SHOW. For instance, LIGHTS OUT, based on the famous radio show, had a host--of original television programing. But Vampira may have been the first horror film host.