He was a victim of the Hollywood blacklist during the HUAC hearings. Although he had already been signed, 20th Century-Fox wanted to remove him from The Day the Earth Stood Still (1951). Producer Julian Blaustein felt that Jaffe was so crucial for the role of the Albert Einstein-like Prof. Barnhardt that he appealed to studio chief Darryl F. Zanuck. Zanuck approved Jaffe for the role, but it was his last Hollywood film until the late 1950s.
His cousin Alma's grandson is NYC amateur comedian Jeremy Jacobs.