Children infected with the coronavirus produce weaker antibodies and fewer types of them than adults do, suggesting they clear their infection much faster, according to a new study published Thursday. Other studies have suggested that an overly strong immune response may be to blame in people who get severely ill or die from Covid-19. A weaker immune response in children may paradoxically indicate that they vanquish the virus before it has had a chance to wreak havoc in the body, and may help explain why children are mostly spared severe symptoms of Covid.