system
Given the following post, respond as if you're commenting on Reddit:
human
Eli5: How come immunization shots that a woman gets earlier in her life don’t carry on/pass that immunity to her children when she gives birth?

E.g. if a woman has a tetanus shot, why does the kid need one? If she has an mmr shot, why does her child need to get one? If the lady also has a shot immunizing herself from chicken-pox, why isn't the child also immune from chicken-pox?

Wouldn't the child be immune from the diseases/ sicknesses that the mother already got her shots for?
gpt
It does and it doesn’t.

While in the womb, and while breatfeeding, antibodies from the mother do pass into the child and give that child extra immunity.

But, those antibodies don’t last forever, and the cells that make the antibodies, B cells, do not pass to the baby, they stay in the mother.

So the babies own immune system needs to be activated later to start making its own antibodies.