JUDY WOODRUFF:

FDA Commissioner Margaret Hamburg today called the recent measles outbreak in the U.S. alarming and said the vaccine should be used by everyone who has not been vaccinated.

More than 120 cases have been reported in 17 states and the District of Columbia since December. Hamburg's comments came after other warnings from public health officials in California, where a report by KQED Public Media told the story from Marin County of unvaccinated children being invited to a so-called measles party for intentional exposure. The mother didn't let her children take part.

But the story underscored anew some of the many questions that have surfaced.

To help get some clarity, I spoke earlier today with Dr. Anne Schuchat. She's the director of CDC's National Center for Immunization and Respiratory Disease.

Dr. Schuchat, welcome to the NewsHour.

There's at least one media report out of California, Marin County, about a mother inviting other parents to bring their children over because the mother's child had the measles. Are you hearing reports like this? What does the CDC know, and what is your recommendation?

DR. ANNE SCHUCHAT, Centers for Disease Control and Prevention: That really scares me. I haven't heard other reports of that.

Parents really need to know that measles can be serious. Many children just have a mild illness, but it can result in pneumonia, dehydration and even encephalitis or death. I would hate for you to expose your child to the virus and end up with one of those outcomes.

So, we really strongly want parents to know that the measles vaccine is safe and effective, and it's the best way to protect your child against this disease.