It's unlikely that anyone is born naturally immune to a novel virus.
The story is about natural exposure to a specific strain of the virus creating an immune response.
Being vaccinated creates antibodies too by your bodies immune system.
Most vaccines at this stage developed to combat the Wuhan strain IIRC.
The 70% vaccinated target is a short to medium term measure as the population transitions to living with COVID.
I think the next step around lockdowns and restriction decisions will be based on the hospitalisation rates until such time as an equilibrium is reached.
