• 種痘しゅとう — smallpox vaccination; inoculation
• 水痘すいとう — chickenpox
• 天然痘てんねんとう — smallpox (full term)
• 痘痕あばた — pockmark; scar left by pox

On the left, 疒 is the illness radical, showing a person lying on a bed. On the right, the part that looks like 豆 gives the sound トウ and also suggests small round spots. Together, 痘 refers to an infectious disease that covers the skin with many pox-like eruptions.