I’ll give Joseph a hint in answering yehudayona’s question about the last time someone contracted polio: it continues to happen, in the backwards parts of the world where there are no vaccines available against polio.
And as far as I know, polio vaccine and smallpox vaccine have reached Boro Park. Williamsburg is trickier – some of the hipsters there are vaccine-averse, but I am pretty sure Williamsburg residents can get vaccinated if they want to.