The republic of Ireland will be grand. Unlike where I am from (the Netherlands), there is no 'bible belt' within the Republic of Ireland. It is known that fundamentalist protestant christians are less likely to get vaccinated. I myself was born in a fundamentalist protestant christian family and even though I am not religious I am also too afraid to get vaccinated. If you have areas where loads of unvaccinated live together, that can be a problem. But the Republic doesn't have that. You might have that in Northern Ireland though (Loyalists) but those people don't tend to travel to the Republic all that much.
The thing is, the benchmark for 'herd immunity' keeps going up as new variants are introduced. We have always known that you can never get literally 100% of the population vaccinated. Never ever, even in the hypothetical scenario where a dictator would commit a gnocide on the unvaccinated there will always be some people who manage to escape.
At some point you will have to learn to live with it and let go.