Um, not dying
Of course! vaccines help prevent getting infected will illness that can serious harm you or kill you.
Think of it this way... A child born in 2011 has a risk of death by age 5 is one in several thousand. A child born in 1911 had a risk of death by 5 of 1 in 5! yes 20% chance. Much of that difference is due to decrease in vaccine preventable diseases.