Final answer:
Sanctifying grace, which is lost through mortal sin, can be restored through confession and repentance, by seeking the sacrament of reconciliation and showing genuine remorse for one's sins.
Step-by-step explanation:
If sanctifying grace is lost by mortal sin, it can be restored through confession and repentance. This belief is rooted in Catholic theology which states that grace, a participation in the life of God, can be regained by seeking the sacrament of reconciliation (confession) and expressing sincere remorse for one's sins, followed by performing the penance given by the priest. Sanctifying grace is said to heal the soul and bring it back into alignment with God. Options such as vaccination or antibiotics are medical treatments and do not pertain to matters of spiritual grace or sin.