Vaccines are among the greatest achievements of modern civilization. They wiped out smallpox, are close to wiping out polio, and have greatly reduced the incidence of a whole slew of other illnesses, extending human lifespans in the process. This infographic by Our World in Data's Max Roser runs down how much immunization has reduced the incidence and death toll of 15 diseases in the United States.
For example, the vaccine for pertussis (a.k.a. whooping cough) has saved the most lives, as the death rate fell from 30.8 per million in 1934–1943 to 0.09 per million in 2004.
Of course, vaccines' impact is even larger globally, with the World Health Organization estimating that they prevent 2 million to 3 million deaths a year. As public debate over the (still relatively rare, thankfully) practice of vaccine refusal grows, it's worth keeping in mind exactly how much immunization has done for public health, and how much we lose when refusal becomes more common: