The vaccine is also free in the US as well, and at this point readily available at most pharmacies as well as doctors offices, urgent care centres, hospitals, etc. etc. A number of sites have also hosted vaccine clinics. A church in Florida recent hosted a clinic after six (unvaccinated) worshipers under the age of 40 died within about a week of each other. This propelled the church to really try and encourage more attendees to get vaccinated.The problem I see with increasing insurance costs for unvaccinated people is that it will encourage the insurance companies to be more avaricious than usual. In a health system such as the US it will give them an excuse to increase costs not just for this, but other conditions and at the same weasel out of paying out when claims are submitted.
In NZ the vaccine is free so there are no cost barriers preventing people getting the vaccination. Also hospital level health care is free and going to the General Practitioner - primary health care, is subsidised. So if you get crook (sick) or real crook, you are covered.