Weird dream. Trying to create herd immunity on an island started with a single infected patient.
So, exactly what is herd immunity and how does it work. In summary, it means in a closed system, the majority of the inhabitants are immune from a sickness which prevented the sickness from spreading across the entire population. Here, majority means 90 to 95% of the total population.
The immunity are achieved by nature cause or vaccination. That is, without vaccinations, immunity can be result of anti-body from existing immune system or generated by host body after getting infected. In any case, the immunity may or may not be permanent, thus why certain vaccines need to be administered once every few years.