The scar from my childhood smallpox vaccination is still there.
Tips
mistakes
种 is read zhòng here, "to plant, to inoculate", not zhǒng. Long before the cowpox vaccine, Chinese doctors inoculated children with matter from smallpox scabs, called 人痘. Jenner's cowpox method, 牛痘, reached China in 1805, and 种牛痘 took its place.