Was there any human person ever preserved from original sin?
Yes, the Blessed Virgin Mary was preserved from original sin from the moment of her conception in view of the merits of Jesus Christ. This privilege is called the Immaculate Conception.
Let me explain it.
Here we have God overlooking all of human history—from creation to the apocalypse, or the end of time. For you and me, time is linear. That is, we can recall what happened a moment ago, anticipate what may happen a moment from now, and experience what is happening right this instant. That's a consequence of nature—the nature as God created it.
For God, though, time is not linear. He can see all of human time from the beginning to the end, all at the same time. In other words, for Him there is no past or future; only the present. He is eternally in the present.
So God looks down on the crucifixion, performed for the redemption of all mankind. It was on the cross that Jesus won the super abundant sanctifying graces necessary to save all mankind. As He views Jesus' sacrifice on the cross, winning our redemption, He also sees the conception of Mary in her mother's womb.
So He reached down, in a manner of speaking, and drew from His Son's super abundant sanctifying graces to apply them to Mary's soul (IC) at the moment of her conception. For us, it appears to be a retroactive action, but for God it is just as present as it is for you who are reading this.
This is how Jesus was given a perfectly clean vessel to grow as He came into the world. This privilege God gave to Mary is called the Immaculate Conception.