Even among the chaos generated by Donald Trump’s recent cabinet picks, one stands out for the extensive suffering and lasting institutional damage it may cause: his choice of Robert F. Kennedy Jr. to lead the Health and Human Services Department.

Modern public health is one of civilization’s great achievements. In 1900, up to 30 percent of infants in some U.S. cities never made it to their first birthday. Since that time, vaccines, sanitation and effective medications have eliminated many previously commonplace illnesses and consigned others to extreme rarity. It’s easy to take much of that for granted, especially as those days have receded from living memory, but those achievements are fragile and can be lost.

The danger isn’t merely that Kennedy — who has almost no experience in government or large-scale administration, and who has shown a sometimes breathtakingly loose connection to the truth — would be incompetent or misleading. At the helm of a department with over 80,000 employees and a $3 trillion budget, one that oversees key agencies such as the Centers for Disease Control and Prevention, the Food and Drug Administration and the National Institutes of Health, he would have control over the nation’s medicines, food safety, vaccines and medical research. With that power he could inflict significant harm to the public health system — and to the public trust that would be needed to rebuild it once he’s gone.

Kennedy has brought attention to some worthwhile public health concerns, such as the downsides of ultraprocessed foods and the value of exercise. But beyond those reasonable issues, he has filled the internet and the airwaves with views on vaccines, food safety, medicines and supplements that are a mix of grave misrepresentations and far-fetched conspiracies.

His opposition to vaccines has attracted the most attention. He doesn’t say just that they merit closer scrutiny, as some “vaccine skeptics” claim. Last year he told a podcaster that “there’s no vaccine that is, you know, safe and effective.” When it later became expedient, he denied that he had ever said such a thing. The truth is that he has long promoted the lie that vaccines cause autism, and the extravagantly false claim that “researchers have done very little to study the health” of children after they get shots for once-common diseases.

Outside of the medical community, few people still know about all the diseases whose safe and effective vaccines he is lying about, so let me remind you about one of them: diphtheria. Once known as “the strangling angel of children,” it causes its young victims to slowly and painfully suffocate, turn blue and gasp as a thick film fills their throat. They lie dying for many agonizing days. The disease has been all but wiped out, but in Spain a few years ago, it cost the life of an unvaccinated boy of 6. His distraught antivax parents promptly vaccinated their surviving child.

Kennedy doesn’t mention those gruesome realities. The core of his method is to mislead and confuse with selective citations that overlook key, even overwhelming evidence. He has falsely suggested that AIDS isn’t caused by H.I.V. With no evidence, he once mused that Covid was deliberately made to target Black and Caucasian people, while ensuring that “the people who are most immune are Ashkenazi Jews and Chinese.” When he was called out for trafficking in racist, antisemitic tropes, he walked the claim back, but only a little.

And throughout it all, he has pursued a course of relentless self-promotion, the consequences be damned. After an incorrect preparation of the M.M.R. vaccine killed two infants in Samoa, Kennedy jumped on the tragedy, spreading misleading information about it on social media.

Over the previous year, vaccination rates on the island had plummeted to less than 30 percent, a decline that has been attributed to vocal antivaccine groups. By the next year, a measles outbreak resulted in about 5,700 cases and more than 80 deaths, mostly among children under 5. It was then that Kennedy traveled to Samoa to meet with some of those activists, after having loudly cast doubt on the M.M.R. vaccine’s efficacy. The outbreak was halted only after the government declared a curfew, with desperate parents instructed to fly a red flag in front of their homes to alert mobile vaccine crews that their children needed shots.

As the head of Health and Human Services, a position that has, as one former secretary, Alex Azar, put it, “a shocking amount of power by the stroke of a pen,” Kennedy could go far beyond making false claims. For example, he could attempt to stop N.I.H. research on infectious diseases, as he recently vowed to do, or take actions that would make vaccines less available and lower their uptake.

And the victims wouldn’t just be children in families that consciously opt out. Many vaccines aren’t available for any children before the age of 6 months, and it takes years to complete the full schedule to get robust protection. That means infants and young kids are extremely vulnerable, as are immunocompromised people, cancer patients and the elderly. Globally, childhood vaccination rates have already stalled, and any further decline could mean outbreaks start happening much more widely.

All of that is bad enough under the best of times. But what if another pandemic rolls around? Here’s what Kennedy has to say about Covid vaccines, the greatest achievement of Trump’s first term: The “powerful vaccine cartel,” which he described as being led by Dr. Anthony Fauci and Bill Gates, worked “to prolong the pandemic and amplify its mortal effects” and “led an effort to deliberately derail America’s access to lifesaving drugs and medicines” such as ivermectin and hydroxychloroquine in favor of their nefarious vaccine project. In fact, both those medications were subjected to rigorous research, and proved to be ineffective against Covid.

If pandemics sound like yesterday’s news, the H5N1 outbreak among the nation’s dairy cattle continues to rage, as does the avian flu version ravaging birds everywhere. And there are strong signs that many human infections are going undetected.

Yet Kennedy has been a vigorous proponent of raw milk, which, unlike pasteurized milk, has been shown to carry extremely high levels of the virus.

As for the legitimate public health issues that many people feel grateful to him for shining a light on, Republican senators could surely reject Kennedy and pressure Trump to find someone else to raise those issues, someone who won’t take a wrecking ball to the precious public health system that protects the nation’s children. Besides, someone who doesn’t respect scientific evidence and can’t tell quackery from credible suspicion isn’t likely to be that much help on those topics.

The Covid pandemic left a lot of people outraged, and some of their anger is justified. The tendency of many Democrats and some public health authorities to circle the wagons and issue blanket denials made things only worse.

We still need a fair reckoning of what went right and what very much did not. But it hasn’t come. Instead, public anger has been stoked, misdirected and exploited by those who seem less interested in solutions than in burning it all down.

Some Republican senators may be tempted to approve Kennedy’s nomination simply because they, too, are angry, or think that some agencies are overdue for a good shake-up.

That would be a grave mistake.