Generally you need 95%+ of the population to be immune to a disease to confer herd immunity anyway, and COVID-19 is so easily transmitted I wouldn't be surprised if it'd take 99%+.
And herd immunity isn't immunity for the individual. All it means is that the disease has great difficulty spreading in a specific population, but if it manages to get into a vulnerable population things can go badly wrong, as we see often enough when things like polio or measles get into an anti-vaccination community and spread like the plagues they are.
And herd immunity isn't immunity for the individual. All it means is that the disease has great difficulty spreading in a specific population, but if it manages to get into a vulnerable population things can go badly wrong, as we see often enough when things like polio or measles get into an anti-vaccination community and spread like the plagues they are.