In countries where vaccines are paid for by the state (partially or fully) doctors won't prescribe them unless there's a statistically significant benefit across the entire population. If it's generally accepted that shingles is more common/risky over 50, guidelines will prevent doctors from offering the vaccine before that age, essentially not to "waste" public money.
In the UK everyone turning 65 is offered the vaccine on the NHS.
The problem is that long term effectiveness generally drops in vaccine. Although we haven't had Shingrix long enough to give great estimates long term evidence of this we have this:
> No Shingrix vaccine booster is currently available.
So if you get it when you are 50, it will be less effective when you are 80 and more vulnerable to shingles. It has nothing to do with "being state funded" and everything to do with giving it to people when they need it rather than wasting it on people who don't, who then can't have it when they actually do need it.
You might want to check with your doctor about that, as that is not what the NCOA is implying.
I would really like to be wrong, as the shingles vaccine is less than £500 privately in the UK for both shots, and that would be worth it to not get shingles.