I have forgotten both the old & new ones already, but I pick up that Stay-Alert is part of the new slogan, although many folk find 'Stay Alert' too vague.
Suppose you were tasked with marketing a new slogan, that was about being allowed to go out (so you need to move away from simple Stay Home). Would you have said...
"Stay safe", "Stay Distant", "Watch out" or ... what?
I like "Stay Distant".