Before a vaccine for smallpox was discovered people used to take recourse in variolation, a process in which those who didn’t yet have the disease were exposed to material from the scabs of smallpox patients. This caused a mild infection, but protected them from contracting the full disease.
![Covid-19: Masks can slow spread and build immunity| Times of India](https://nanofiberindia.com/wp-content/uploads/2020/11/Screenshot-2020-11-26-at-1.14.45-PM.png)
![Covid-19: Masks can slow spread and build immunity| Times of India](https://nanofiberindia.com/wp-content/uploads/2020/11/Screenshot-2020-11-26-at-1.14.45-PM.png)