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 Robert F. Kennedy Jr. has long questioned the safety and effectiveness of many vaccines. And President Trump recently called for big changes in how children get vaccinated.
"They pump so much stuff into those beautiful little babies it's a disgrace. I don't see it. I think it's very bad," Trump said recently at a White House event. "It looks like they're pumping into a horse."
So a powerful Centers for Disease Control and Prevention committee hand-picked by Kennedy is now scrutinizing the childhood vaccine schedule. The schedule is the finely calibrated timetable pediatricians use to administer the sequence of more than 30 doses to protect against more than a dozen diseases.
The move is being welcomed by some advocates, physicians and scientists.
"I think it is true that any vaccine schedule should periodically be assessed," says Dr. Ofer Levy, a vaccine scientist at Harvard. "As we like to say, 'Moses did not come down from Mount Sinai saying: 'This will be the only way that you immunize.'"
But others worry the review is part of Kennedy's campaign against vaccines.
"Robert F. Kennedy Jr. has for 20 years been an anti-vaccine activist and science-denialist. You would have hoped that when he was confirmed as secretary of Health and Human Services he would have taken on his job, which is to protect the health of children in this country. But he didn't," says Dr. Paul Offit, who runs the Vaccine Education Center at the Children's Hospital of Philadelphia. "All he cares about is making vaccines less available, less affordable and more feared."
Federal officials did not respond to NPR's questions about a possible overhaul of the childhood vaccine schedule.
The scrutiny is especially troubling to many public health authorities, coming amid new outbreaks of diseases like measles and whooping cough. These are on the rise because of falling immunization rates.
Offit and others say every vaccine is meticulously evaluated before being added to the schedule. And researchers and regulators continually monitor all vaccines.
"All the data and evidence suggest that our vaccine schedule is incredibly safe and incredibly effective," Dr. Yvonne Maldonado, a pediatric infectious disease expert at Stanford University. "In fact, it is probably the most effective vaccine schedule in the world."
Kids get this roster of shots at a young age to make sure they don't catch dangerous diseases when they're most vulnerable, Maldonado and others say.
Some people who are worried about vaccines argue the number of different antigens and other ingredients could overwhelm a child's immune system. But babies' immune systems can handle it, says Maldonado and other scientists. Children are exposed to far more stimulation naturally from microbes than from vaccines. And vaccines have been refined over the decades to minimize the number of ingredients they contain.
There are about 170 different components in the various shots in today's vaccine schedule, Offit says, which is "actually less than the vaccines that Robert F. Kennedy Jr. and I got as children of the early 1950s," Offit says.
Experts are especially alarmed that the CDC is investigating splitting up the MMR vaccine, which protects kids against measles, mumps and rubella in one shot. Giving kids three separate shots would mean more trips to the doctor and more needles, vaccine proponents like Offit say. They worry that, inevitably, more kids would end up missing vaccines. And it would take years to develop new individual shots, according to the proponents.
Dr. Jesse Goodman, a vaccine expert at Georgetown University who used to regulate vaccines at the Food and Drug Administration, says: "It's as if you had this really winning football team and you said, 'Well, gee, we're winning. We win every season. We win every game. Let's change everything we're doing."
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