Whooping cough. Mumps. Polio.

Thanks to widespread vaccination, diseases like these that once killed thousands of Americans each year have become so rare in the U.S. that most younger doctors have never seen a case in-person.

But that could change if enough people stop vaccinating, according to many of the doctors, ethicists and public health officials FRONTLINE spoke with in The Vaccine War — a newly updated version of our 2010 documentary that airs Tuesday, March 24 on PBS stations and online.

That’s why Portland, Oregon-based pediatric intensivist Dr. Cynthia Cristofani has made it her mission to document the rare cases of vaccine-preventable illness that she’s come across over the years — and to use the footage to teach other medics how to recognize these diseases and educate parents on what they entail.