Measles is a highly contagious disease caused by a virus. It spreads through the air when an infected person coughs or sneezes. It can be very serious and cause hospitalizations, serious health complications and even death.
Before the measles vaccination program started in the U.S. in 1963, an estimated 3 million to 4 million people in the country got measles each year. Prior to the introduction of the vaccine, 48,000 people were hospitalized due to measles and nearly 500 died each year. Since then, widespread use of the measles vaccine has resulted in a greater than 99% reduction in measles cases and deaths compared to the pre-vaccine era. But outbreaks related to vaccine hesitancy have been occurring worldwide in recent years. In the U.S., more than 1,600 cases of measles have been reported so far in 2025, the most number of cases since measles was declared eliminated in the U.S. in 2000.