See for example https://fivethirtyeight.com/features/unvaccinated-america-in...
There’s a pretty stable “never” population at 14%, and you see that as time goes on the hesitants have been gradually been getting won over.
I’m sure some in the “never” camp are using “it’s not been approved” as their current first-line given reason. But I think you need to break down the groups a bit more. There are genuinely people who are not fundamentally anti-vax that are just nervous about how fast the vaccines were developed or scared about what having “RNA” in the vaccine means (I don’t share these concerns but I understand where they come from). Some of these people will at the margin be persuaded by things like full approval.