So Jesus said to them, "Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink His blood, you have no life in you; he who eats My flesh and drinks My blood has eternal life, and I will raise him up at the last day. (John 6:53-54)

After being baptized and chrismated, the newly illumined is given Holy Communion. From the very beginning of the Christian faith, all Christians receive the Precious Body and Blood of Christ, regardless of their age or intellectual maturity. This includes infants, who have just received Baptism.

Just as a baby born in America, though knowing nothing of being an American, receives all the rights, and protections of every other American citizen, so too, every citizen of heaven receives the fullness of the Kingdom of heaven.

Baptism is a great mystery.

A mystery is not something we can't know anything about.
A mystery is just something we can't know everything about.
And we are comfortable knowing that we don't know everything about God, ourselves, and the Kingdom of heaven.

That is what it means to be Orthodox. To love and worship a God Who is greater than your ability to ever fully comprehend Him, and be comfortable knowing you don't know.

Baptism, Chrismation, and Holy Communion are the initiatory mysteries for those who are preparing for a life of Discipleship to Jesus Christ.