https://www.overclock3d.net/news/software/call_of_duty_vanguard_s_technology_will_fix_the_series_storage_issues/1
 
Call of Duty: Vanguard will be offering PC gamers, and current-generation console players (Xbox Series X/S and PlayStation 5) users access to a new "on-demand texture streaming" technology that is said to reduce the game's install size by 30-50%.

Gamers on all platforms have been complaining about Call of Duty's install sizes for years now, with Call of Duty Warzone updates frequently weighing in at 50+ GB. Warzone alone can occupy over 130GB of HDD/SSD space, making the game a primary reason for storage upgrades for many PC/console storage upgrades. 

Sadly, Call of Duty Vanguard's storage requirements are currently unknown, so we cannot comment on whether or not the game will require you to purchase a new HDD or SSD to play it. That said, it is clear that last-generation console users will be getting access to a version of Vanguard that's larger than the game's PC/current-gen console counterpart. Thankfully, we do know that the game's "install size at launch will be significantly below previous Call Of Duty releases."

At this time, it is unknown what technology is being used to compress Call of Duty Vanguard's PC and current-generation console versions. Some have speculated that this technology uses internet streaming for some assets, though this technology is more likely to be based on asset compression and the powerful decompression capabilities of modern PCs and consoles. 
 
Any effort to reduce the install size is welcome.