Since the beginning of the year, a measles epidemic has been sweeping the United States; what started as an outbreak at Disney’s resort in Anaheim has now led to more than 150 cases in 17 different states. Measles is an extremely aggressive and highly contagious respiratory virus—it gathers in the trachea so that every time its host coughs it will be propelled into the open air. What is perhaps more astonishing than the rate at which it can spread is the simple fact of how easily preventable it is.

According to the Center for Disease Control and Prevention a single dose of an MMR (measles, mumps and rubella) vaccine is 93% effective in preventing measles, a second dose can increase that effectiveness to 97%. Recent polls show that most doctors believe that the recent outbreak could have been completely avoided if parents had simply vaccinated their children.