Ben Carson’s sins against science during last week's Republican Presidential debate may have been even worse than Donald Trump’s. PHOTOGRAPH BY FREDERIC J. BROWN / AFP / GETTY

Republican candidates for President seem unable to shake the habit of making wildly reckless comments about science and public health. Michele Bachmann remains responsible for perhaps the most remarkable of these statements, when, in opposition to all known facts, she told Fox News, after a 2011 debate, about a girl who had “suffered mental retardation” as a result of receiving the HPV vaccine. Last week, though, Donald Trump solidified his place in the circle of scientific ignorance when he drew his own connection between vaccines and autism. “We've had so many instances, people that work for me,” he said, and described a “beautiful child” who, according to Trump, had recently been vaccinated, fallen ill, and “now is autistic.” Trump claimed that if vaccines were spread out, “I think you're going to see a big impact on autism." Trump has repeatedly expressed his view that vaccines cause autism. In 2012, he tweeted that “massive combined inoculations to small children is the cause for big increase in autism.”

I have written many times that possible links between vaccinations and autism have been researched widely and have never been found to exist, and that words like Trump’s are dangerous—and even deadly. And I am far from alone. The comments came at a particularly bad time, because the Centers for Disease Control and Prevention had just begun its annual attempt to convince Americans to get flu vaccines, which, while not always perfectly effective, are safe and far better for both individual and public health than not getting vaccinated. (It has always been hard to know precisely how many people die of the flu in this country each year, but the number is in the thousands.) Federal officials say that this year’s vaccine is almost certainly going to be more effective than last year’s. But, thanks to our nationally televised lunacy, the job of convincing people to get them just got harder.

Trump is terrifyingly popular, but we have come to expect dangerous inanities from him. Ben Carson, however, is another story. As a world-renowned pediatric neurosurgeon who retired after many years at Johns Hopkins, his sins against science during the debate were perhaps even more outrageous than Trump’s.

Carson’s first comment on the subject made him sound like a responsible, educated physician: “There have been numerous studies and they have not demonstrated that there is any correlation between vaccinations and autism.” One cheer. Then things went south: “Vaccines are very important, certain ones—the ones that would prevent death or crippling,” he said. “There are others, a multitude of vaccines, which probably don’t fit in that category, and there should be some discretion in those cases.” And: “A lot of this is … is … is pushed by big government.”

What on earth was he talking about? Today, the C.D.C. advises that American children be vaccinated for fourteen diseases before age six—and each of those diseases can, in Carson’s infelicitous words, cause “death or crippling.” “The only one you could reasonably say does not kill is mumps,” Paul Offit, a physician in the division of infectious diseases at the Children’s Hospital of Philadelphia, told the Times last week. Offit, who is among the nation’s most outspoken vaccine advocates, added that mumps can, however, cause permanent deafness and sterility in men after puberty. “Tetanus kills, rubella kills unborn children, measles kills, hepatitis B virus kills,” Offit said.

But Carson was just warming up, because what he said later was even worse: “It is true that we are probably giving way too many in too short a period of time.” With that, Carson added his voice to the rallying cry of “too many too soon,” uttered reflexively by the anti-vaccine crowd. This notion, that the vaccine schedule for children has become so crowded that it puts extra pressure on their immune systems, is immensely popular among American parents—and, increasingly, pediatricians are yielding to their requests to delay vaccines.

This, too, is dangerous. As Tara Haelle pointed out in a particularly useful post at Forbes.com, delaying vaccines just prolongs a child’s risk for preventable diseases. The data could not be clearer. And, despite the increase in scheduled vaccines, children are exposed to far fewer antigens than ever before. As many people (including me) have written, the smallpox vaccine—which we stopped administering after the disease was eradicated, in the nineteen-seventies—contained two hundred proteins. When counted all together, the fourteen vaccines that children receive today contain no more than a hundred and fifty.

The only other trained medical professional on the stage also failed his biology (and public-service) tests last week. Rand Paul, an ophthalmologist, said, “I’m all for vaccines. But I’m also for freedom.” He seemed to care more about repeating that political conceit than about the lives of his constituents. He agreed with Carson that vaccines were “too bunched up.”

It is sad to have to write this, when it should be clear by now, but here it is: vaccines are the most successful medical intervention in the history of humanity. They have prevented millions of deaths. They are a triumph of human ingenuity and of our desire to alleviate suffering.

There are not too many. They are not administered too soon. They do not cause autism or allergies or cancer. The only thing “too bunched up” about vaccines, as a matter of fact, are the falsehoods and deliberate misconceptions spread by demagogues and then endorsed by people like Carson and Paul, both of whom should—and almost certainly do_—_know better.