Vaccines save lives. Measles vaccines alone are estimated to have prevented over 21 million deaths between 2000 and 2017. Vaccines will help protect your child against diseases that can cause serious harm or death, especially in people with developing immune systems like infants. It’s important to vaccinate your child. If not, highly contagious diseases such as measles, diphtheria and polio, which were once wiped out in many countries, will come back.