Ugh, this nonsense again. It's meaningless posturing. No one tests for proof of herd immunity. No vaccine is tested to prove that. There's no reason to. You test efficacy and safety.

If it's efficacious, you can calculate what percentage of the population you need to make immune to provide various thresholds of protection for those who cannot be vaccinated.

Again, no one does this kind of test because we assume that the immune system works.