The deaths in Pennsylvania are the state’s first from the disease in 35 years. Experts warn that declining vaccination rates have opened the door for resurgence of disease once largely eradicated. Key points and original sources are listed below.

• The deaths in Pennsylvania are the state’s first from the disease in 35 years. Two weeks ago, Donald Trump claimed the measles, mumps and rubella vaccine could be “quite lethal”.S1

• Experts warn that declining vaccination rates have opened the door for resurgence of disease once largely eradicated.S2