Despite the rarity of diseases like polio and diphtheria in the U.S., recent cases underscore that these threats persist when immunization rates decline. Meanwhile, more common infections like pertussis and hepatitis B continue to pose serious risks to unprotected children. Here to talk about the importance of timely and routine childhood vaccination is Dr. Paul A. Offit, Director of the Vaccine Education Center and a Professor of Pediatrics in the Division of Infectious Diseases at Children's Hospital of Philadelphia.