Premium Surcharge for Unvaccinated Spouses/Dependents

I'm trying to better understand the potential HIPAA discount/surcharge issues where spouses and dependents are involved (setting aside ADA, GINA, etc. for the moment). 

Is it permissible to require all covered individuals (or perhaps at least spouses and adult dependent children) to be vaccinated to receive the discount (or avoid the surcharge)? I don't see the nondiscrimination regulations drawing a clear distinction, other than allowing the 30% incentive limit to be determined based on the cost of coverage including spouses/dependents where the spouse/dependent is also eligible for the incentive.

Or if the employee alone (or spouse alone) gets vaccinated, do you have to extend a partial incentive based on their individual compliance with the requirements?

Any input would be greatly appreciated.