Parents who delay or skip childhood vaccinations even when kids have no medical reasons are contributing to U.S. outbreaks of measles and whooping cough.

Actor Robert De Niro made national headlines in March when he pulled a controversial film about vaccines from the Tribeca Film Festival.

The film Vaxxed was directed by Andrew Wakefield, the author of a study published — and later retracted — by the medical journal The Lancet that purported to have found a now widely debunked link between vaccines and autism. Editors of the journal later said “it was utterly clear, without any ambiguity at all, that the statements in the paper were utterly false.” Wakefield also lost his license to practice medicine in the U.K.

De Niro, who founded the festival, made his decision less than two weeks after JAMA published an exhaustive analysis of recent measles and pertussis outbreaks.

The U.S. experienced a record 667 measles cases from 27 states in 2014 that included a multi-state outbreak traced to Disneyland — the greatest number of cases since the Centers for Disease Control and Prevention declared the disease eradicated in 2000.

The study’s conclusion: Vaccine refusals are to blame.

Former C.S. Mott Children’s Hospital pediatrician Matthew Davis, M.D., wrote an accompanying editorial for the JAMA piece and explains the significance of the findings below.

Read the full article here.