Devil's advocate here; to me it sounds like he was about to say "kids" instead of children and his accent made it sound like he said "to give boosters to kill children."

The "ki" in kids and the "il" in children turned into "kill" as he was looking for the proper word.

Could be a Freudian slip, sure, but I think this is just a case of a tongue-tied person with English as a secondary language mixing up two words.