Vomit smell is very difficult to remove from walls. Mix together hydrogen peroxide and baking soda, apply on the wall and leave for about 20 minutes before wiping.
The combination of hydrogen peroxide and baking soda will cause an exothermic reaction that breaks down the proteins in vomit to form carbon dioxide gas, water, urea, ammonium hydroxide, ammonia, and other compounds that have no smell or flavor.