The Dept. of Health and Human Services (HHS), starting in 1988, was supposed to report every two years to the Congress, on ongoing efforts to improve vaccine safety. NO REPORTS WERE EVER MADE.
So…why didn't they follow the law?
One: Arrogance. Federal agencies will, when they think they can get away with it, ignore a law entirely. They'll pretend it doesn't exist.
Two: Following the law would have constituted a de facto admission that vaccine safety is a problem. If you need to update your efforts in that direction every two years, there is a serious problem. The federal government does not, under any circumstances, want to admit vaccines cause widespread harm.