I now have the H1N1 vaccine in my body, running around stimulating my immune system, in a "fake fight" that will prepare my immune system for the real thing. And this got me to thinking about how religion does the exact same thing, but via ideas (memes) that it uses to inoculate the young against atheism and "false" religions.
One of the cool things about studying religion via cultural evolution, called "memetics" (the application of Darwin's "survival of the fittest" to ideas as they move across society and down through history) is that religion exhibits all of the same survival mechanisms as biological life, including a robust immune system. Just as your body reacts to threats, so does religion.
How do you keep a child from "catching" a religious "disease," that is, from straying from your faith? It's simple. Starting from an early age, you have to implant immunity "memes" (ideas) into the child, ideas that make the child resistant to the "disease" (other religions, or atheist ideas).
There are two parts to this immunity: First, you teach the child that your religion is great and wonderful, and that the rewards for staying on the "true" course are magnificent. And second, you teach your child that the other religions are false, and that if the child strays from your path, unimaginable punishment awaits.
Once these ideas are implanted in the child, it becomes very hard indeed for any other ideas to infect the child. He or she can be turned loose into adult society, and will resist all other religious infections for a lifetime.
It's critical to get my H1N1 vaccine before the disease strikes, because without immunity I'm likely to fall victim to the virus. And not surprisingly, this is also true of religious immunity: If you wait too long, the child might be infected by the wrong memes (other religions, or even atheist memes) before you've had a chance to develop the child's immunity via your own memetic inoculation.
That's why all major religions have highly-developed programs to teach children starting from a very young age. It's never too early to begin the religious indoctrination. To those of us who study memetics, it's exactly parallel to the H1N1 inoculation that is now circulating through my body.