For decades, babies have been wincing, squirming and crying their way through a series of vaccinations that start as soon as they're born. The shots protect against diseases such as diphtheria, tetanus and mumps, which once plagued children and their parents.

"When I was a kid, my parents were terrified about my catching polio or measles or whatever. And friends of mine died," says Dr. Stanley Plotkin , a veteran vaccine scientist who is now 93 and a professor emeritus at the University of Pennsylvania.

"A parent today very likely does not worry about his or her child dying of an infectious disease," he adds.

That's because routine childhood vaccinations have largely vanquished many diseases, making vaccines one of medicine's greatest triumphs.

But Health and Human Services Secretary

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