Back to Basics: Vaccination Against Original Sin

This is probably the simplest explanation I've ever seen of how baptism fights original sin.

Catholicism sees original sin differently from actual sin, which is what a rational person does when she consciously, deliberately, and willingly disobeys God. Original sin is the natural inclination to sin.

For example, nobody is born with polio, measles, or chicken pox, but folds aren't born with any immunity to these diseases, either. A baby needs to be vaccinated, so the human body can produce its own antibodies and fight these diseases when it's exposed to them. Likewise, you can think of original sin as being born without any immunity or ability to internally fight sin. On the spiritual level, human beings, born without any resistance to sin, need a spiritual vaccination.

Baptism is to original sin what the polio vaccination is to the poliovirus. Baptism restores what should have been -- a spiritual resistance or immunity to sin and temptation. The first sin of the first parents, Adam and Eve, wounded human nature, and every one inherited that wounded nature from them. Baptism washes it away.

... And just as vaccinations are but a first step for a healthy physical life, Baptism is but a first step for a healthy spiritual life. Cultivating a good, healthy spiritual life means avoiding what's bad for your soul, such as sin and evil, and doing what's good for your soul -- prayer and works of mercy motivated by divine grace.

In addition to getting rid of original sin, Baptism also imparts or infuses sanctifying grace, a special free gift from God. Sanctifying grace makes the new Christian a child of God and applies the merits of Jesus Christ, his suffering and death for sins, to the new Christian personally, because the person being baptized is mentioned by name ...

Catholicism for Dummies by John Trigilio