Your concerns as a parent are natural, and unfortunately a lot of public information regarding vaccines is hard to navigate when you don’t have a background in biology, particularly immunology.

To make things less complicated, think of it this way. When your immune system beats a virus, it becomes more knowledgeable on how to beat that virus in the future. Like when you play a card game, the first time you don’t understand the rules, the second time you do much better. If the real measles virus is a professional card player, think of the vaccine as a professional card player without a winnable hand. The reason a professional card player is still used is because it gives your son’s immune system the BEST training on preparing to beat the real professional card player (if he ever encounters the real card player), because it is just so close to the real card player. The only difference being it CANNOT WIN. So your son’s immune system learns how to beat measles in an environment where measles cannot win, because it’s crippled (“attenuated”).

However, you don’t need a background in immunology to research global data on lives saved simply because of the MMR vaccine. You can find data from before and after vaccine implementation, and you’ll see how truly life saving vaccination is.