If that was their objection, they should have been a qualified yes.
The good news is that COVID is probably no more deadly for the under 18s than flu. Perhaps less so as it is not even clear that it is catching for most youngsters.
It may be deadly for people with existing conditions who are under 18, but then flu may be also. And for them, herd immunity via mass vaccination may be the best policy. If they are not exposed by a third party, they won't catch it.
It's a damn shame that no one trusts anything coming out of America until Trump's people have been removed from participation up and down the chain.