Below is a relevant passage from your source:
If children don’t frequently experience severe illness with COVID-19, why do they need a COVID-19 vaccine?
While rare, some children can become seriously ill with COVID-19 after getting the virus that causes COVID-19.
A COVID-19 vaccine might prevent your child from getting the virus that causes COVID-19. It also may prevent your child from becoming seriously ill or having to stay in the hospital due to the COVID-19 virus.
Might! May! I am sorry to tell you, but anyone with some sense of words understand immediately that the authors of the above passage are quite unsure about the usefulness of Covid-19 vaccines for children.