For domestic travel, they were never required.
For overseas travel, it was either 3 shots or negative RNG "test" which is not a test result, but never a hard requirement.
So in a way, Japan went from 2nd most strict (behind CHAINA!!) border policies to somewhere between the American and European extremes.

But I expect Japan to go to European level after they move the level from 2-atsu (they created a special category just for covAIDS) to 5, which is what Europe did last year too.
Besides, nobody even cares about the covAIDS here anymore anyway, most people are just patiently waiting for the government to say "OK children, it's OK to not be afraid anymore".