Two people have died of measles in Pennsylvania, the state’s health department confirmed Tuesday.

Both people were unvaccinated. They are the first such deaths in the U.S. this year, and the first in the Commonwealth of Pennsylvania in 35 years.

“Because measles was largely eliminated in the Commonwealth for more than three decades, people are not familiar with this disease and don’t fully understand the potential severity of the illness,” Pennsylvania Secretary of Health Dr. Debra Bogen wrote in a statement. “As a physician, I want to make sure that people understand that the MMR vaccine is safe and provides the best protection we have against measles.”

The people who died lived in Lancaster County, which has seen the majority of measles cases in the state’s growing outbreak. As of Tuesday, 393 cases had been confirmed. Eighty-six had been diagnosed in the past week.

So far 70 people in the state have been hospitalized for measles complications.

According to the Centers for Disease Control and Prevention, 2,777 measles cases have been reported nationwide this year, the highest number in 35 years in the U.S. The majority of infected people are unvaccinated, according to the CDC.

Three people died of measles last year, an adult in New Mexico, and two young girls in Texas.

The measles mumps rubella vaccine, given in two doses around age 1 and age 5, offer 97% protection against measles, usually for life.