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?

Question

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?

In: 108

Answer 1

It’s sort of like having the weapons but not the soldiers in an war.

Fetuses can and do get the “weapons” from the mother to fight infections and immunity can pass from mother to fetus. For example the tetanus shot is now administered in something called the “dtap” which immunizes you against multiple illnesses and pregnant women are recommended to get that shot during pregnancy, specifically to pass the immunity to the children. Chicken Pox as well, the “weapons” will pass to the fetus.

The issue is the fetus’s immune system, it’s “soldiers” remain naïve to the illness and don’t receive the training on how to use or maintain the “weapons” and over time the child looses the protection as the “weapons” become useless.