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.
SIMON: And let's begin with mumps. Officials in Ohio say it's the largest outbreak since the forties. How can that happen?
SCHAFFNER: Mumps vaccine, although a very good vaccine, is not a perfect vaccine. And it's about 80 percent - 85 percent effective if mumps is reintroduced into a population. And so what we're seeing here is largely people who have been vaccinated, but now that mumps has been imported into the United States - into that population - it's spreading slowly in that group and it's difficult to contain.
SIMON: What about the decision that some American parents have made not to vaccinate their children? Do you think that contributes?
SCHAFFNER: Not so much to the mumps outbreak, but it does contribute to the measles problem that we're having. The measles outbreaks are clearly occurring in populations whose parents have withheld their children from immunization. They remain susceptible.
Some of those children then travel abroad, encounter measles, bring it back into the United States. They become ill and then it spreads among other unvaccinated children. And those children frequently live in similar neighborhoods or attend the same schools.
SIMON: How dangerous are mumps and measles? Could you remind us?
SCHAFFNER: Well, let's start with measles. Even our medical students are amazed to learn that before we had vaccine, in the United States each year some 400 to 500 children died of measles and its complications. So it's a very, very serious illness. Mumps obviously is a painful illness.
It also can be associated with encephalitis on occasion and on occasion with inflammation of the testicles in boys and the ovaries in girls. It can also have consequences of deafness as a long-term sequel of mumps. So neither are trivial and both in individuals can be very, very serious.
SIMON: Doctor Schaffner, is there something that people and parents can do if the vaccination is only partially successful? Is there something that should be added to that regimen?
SCHAFFNER: Well, what happens now is in these instances of importation, we give a third dose of the mumps vaccine to try and contain such outbreaks. And it's difficult to kind of stay ahead of the virus in identifying the population that ought to have this additional immunization. Although not a perfect way to end the outbreak, it's the best means that we have currently available.
SIMON: Doctor William Schaffner is a professor of Preventive Medicine at Vanderbilt University. Thanks much for being with us.
SCHAFFNER: My pleasure, Scott. Transcript provided by NPR, Copyright NPR.