From the article:
Notably, it has not taken the U.S. eight months to reach this ugly milestone. By May, the country had already seen 288 cases of measles – the most in a five-month period since 1994, and more than had been reported for a given year in well over a decade. The cause for the resurgence is as unambiguous today as it was then. To quote Dr. Anne Schuchat, assistant surgeon general and director of the CDC’s National Center for Immunization and Respiratory Diseases: “The current increase in measles cases is being driven by unvaccinated people.”
The harmful effects of vaccine-refusal have not been limited to measles’ comeback. California, the most populous state in the U.S., has become a case study in what happens when people decide against vaccinating their children. The L.A. Times reports California parents today are opting out of vaccinating their kids at twice the rate they did seven years ago. State health officials say insufficient vaccination has contributed not only to the the widespread reemergence of measles, but the ongoing whooping cough epidemic, and has left the state vulnerable to outbreaks of other serious diseases.