491 Through the centuries the Church has become ever more aware that Mary, "full of grace" through God, was redeemed from the moment of her conception. That is what the dogma of the Immaculate Conception confesses, as Pope Pius IX proclaimed in 1854:

The most Blessed Virgin Mary was, from the first moment of her conception, by a singular grace and privilege of almighty God and by virtue of the merits of Jesus Christ, Savior of the human race, preserved immune from all stain of original sin.

Most holy Virgin, who wast pleasing to the Lord and became His 
Mother, immaculate in body and spirit, in faith and in love, look 
kindly on the wretched who implore thy powerful patronage. The 
wicked serpent, against whom was hurled the first curse, continues 
fiercely to attack and ensnare the unhappy children of Eve. Do 
thou, then, O Blessed Mother, our queen and advocate, who from the 
first instant of thy conception didst crush the head of the enemy, 
receive the prayers which, united with thee in our single heart, 
we implore thee to present at the throne of God, that we may never 
fall into the snares which are laid out for us, and may all arrive 
at the port of salvation; and, in so many dangers, may the Church 
and Christian society sing once again the hymn of deliverance and 
of victory and of peace. Amen.

Novena to the Immaculate Conception