No, it is not necessary to run the Scan process on a set of files before running the Inoculate process on them. The default behavior of LinkFixer Advanced is to automatically scan all selected files prior to running the Inoculate process. The same is true with other LinkFixer Advanced processes including the Cure, Move/Rename and Modify Links processes.
LinkFixer Advanced does provide the option to only Inoculate files that were previously scanned or to Inoculate all files based on your folder selection. This option can be accessed under the "hamburger" menu | Settings | Inoculate tab.