I know a child who has gotten all of her vaccines, but she caught one of the diseases that she was vaccinated against. Doesn't that show that these vaccines don't work?
No. It’s true that occasionally children will not have a response to vaccines. But in 85% to 98% of cases, the vaccines are effective.
Sometimes the vaccines don’t totally prevent the infection but weaken it so the child gets a mild case. This is especially true with influenza and chickenpox vaccines. Most people who get the full-blown disease have not received the full series of immunizations against that infection.