Vitamin A should not be used to prevent measles and large doses of it can cause serious health problems. Pediatrician Edith Bracho-Sanchez breaks down what you need to know about vitamin A and measles and reminds parents that the only way to prevent measles is by getting the MMR vaccine. Two doses of it are 97% effective in protecting children from the virus. Talk to your pediatrician with questions about measles or the MMR vaccine. | American Academy of Pediatrics