It kind of looks like a little book. It's a rectangle with dashes on the side that represent the spirals of a notebook. There's a cross right on the front. Like the red cross. Or a Templar shield.
This Health Book icon is made in Material Design style
developed by Google. This style is based on extremely simplified shapes, thin two-pixel lines, and is optimized for 24x24 px. Unlike other vector icon packs that have merely hundreds of icons, this icon pack contains 6,200 icons, all in the same style and quality.