A MTHRFR gene mutation can make it impossible to.dump a toxic load, so

Kid A has no mutation, gets a shot, developed antibodies and detoxed. Healed before next shot.

Kid B has a mutation. They get the shot and the antibodies but never dump the toxins, so next shot doubles the load. A year later a 3rd shot triples it. Heavy metal poisoning at the least.


Now from what ive read it dramatically about 1 in 600 kids (everyone is damaged just not all terribly and obviously)

the place where I had my kids delivers about 6k every year.