American vaccines that transformed public health over 250 years: 'Outweighs harm'

Before the first successful vaccine was developed in 1796, Americans had little protection against deadly infectious diseases like smallpox, measles and diphtheria.

Over the next 250 years, vaccines helped eliminate or dramatically reduce many vaccine-preventable infectious diseases, preventing millions of illnesses, infections and deaths.

"There is a reason that vaccines are widely considered to be the greatest public health tool after sanitation," Fox News senior medical analyst Dr.