SCOTT SIMON, HOST:
More than 90 percent of American toddlers get the MMR vaccine. It protects against measles, mumps and rubella. But in Ohio, more than 350 cases of mumps have been confirmed this year. And the CDC has said that measles cases are at their highest in two decades.
To try and find out why and how these viruses are spreading, we're joined by William Schaffner. He teaches preventive medicine at Vanderbilt University. Professor, thanks for being with us.
WILLIAM SCHAFFNER: My pleasure, Scott.