Robert F. Kennedy Jr., President Donald Trump’s nominee for secretary of Health and Human Services, is a longtime conspiracy theorist and anti-vaccine activist. He thinks Anthony Fauci and Bill Gates are leaders of a “vaccine cartel” that intentionally prolonged or even started the coronavirus pandemic in order to promote “mischievous inoculations.” Kennedy also blames immunizations for autism and obesity (among other chronic diseases) in children. In the meantime, he isn’t really sure whether HIV causes AIDS, or whether vaccine-preventable diseases such as measles are actually dangerous.

As a doctor, I have spent years following—and fighting—anti-vaccine falsehoods. Along the way, I’ve learned an important lesson: Despite RFK Jr.’s fringe beliefs, he often seems to make sense. Kennedy’s defenders celebrate his fondness for, and facility with, evidence. His real talent, though, is for the clever manipulation of facts. Kennedy is not just a conspiracy theorist; he’s a very good conspiracy theorist. When his confirmation hearing starts on Wednesday, we can expect that he will do what he’s always done, which is to apply a veneer of erudition to nonsense. He may even come off as almost … reasonable.

To witness how this works, read the letter he sent to the prime minister of Samoa on behalf of the anti-vaccine nonprofit Children’s Health Defense in November 2019, during that country’s deadly measles outbreak. Kennedy offers his condolences for the tragic deaths of “precious Samoan children,” and then suggests the need to study the outbreak carefully, so as to “thoroughly understand its etiology.” What might have caused thousands of Samoans to get sick? The letter poses two possibilities: “It is critical that the Samoan Health Ministry determine, scientifically, if the outbreak was caused by inadequate vaccine coverage or alternatively, by a defective vaccine.”

At first glance, and for nonexperts, this letter may appear well reasoned and well sourced. It weaves in historical elements and biomedical data, and includes a list of peer-reviewed references at the end. The letter’s main request—that Samoan officials do nothing more than perform genetic testing on the circulating virus—sounds prudent. Prior research has indicated that vaccinated individuals may shed the virus and infect others, the letter says. Wouldn’t it be good to know if that produced the outbreak?

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In reality, of course, the epidemic was caused not by the vaccines but by the lack of them. (A vaccine-administration accident the year before had produced a scare that led vaccination rates to decline dramatically.) Although the letter’s implication that vaccines were to blame seemed wrong on its face, only when I dived into the cited scientific articles could I see the problems with its details. Kennedy incorrectly claims that genetic sequencing of a large measles outbreak in California from about four years prior found that at least one-third of the cases were due to the vaccine. “Alarmed CDC officials documented this emerging phenomenon,” he wrote. The referenced articles show this to be a fundamental misrepresentation. Although they do describe how the vaccine may, in rare cases, produce a dangerous case of measles, they specifically note that there is no risk of its being transmitted to another person. The genetic testing that Kennedy referenced is used, in part, to distinguish among people who have experienced mild vaccine reactions such as rash and fever from those who have true measles infections. This is important during active epidemics when public-health officials are widely immunizing people, while at the same time trying to isolate infectious individuals. (Kennedy’s press team did not respond to emailed questions about his letter to Samoa, or about other issues with his credibility that are raised in this article.)

A complete refutation of the Samoa letter would run many pages. That may be the point. With his ample, erroneous allusions to scholarship and appeals to authority, Kennedy has perfected the art of the Gish Gallop: a debate strategy in which the speaker simply overwhelms the listener with information, not all of it true. Kennedy’s skill at flooding his audiences with specious claims that sound logical or highbrow was on full display during his 2023 interview with the podcaster Joe Rogan. Over the course of three hours, Kennedy regaled the host with stories about vaccine safety, Albert Camus, Wi-Fi radiation, and the sexual health of frogs, among other subjects. He offered up a bounty of scientific arguments: The words study and studies came up 70 times during the conversation. And, as he has done elsewhere, he encouraged the audience to fact-check everything he said. “Nobody should trust my word on this,” he declared. “You know, what I say is irrelevant. What is relevant is the science.”

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Most of Rogan’s listeners—like most U.S. senators—aren’t likely to have the scientific expertise to assess each of his claims, and certainly not in real time. I caught some errors in the Rogan interview only by virtue of my medical training. For example, Kennedy criticized the inclusion of the hepatitis B shot in the childhood vaccine schedule. The virus is primarily a problem for intravenous-drug users, prostitutes, and homosexuals, he suggested. “Why would you give it to a one-day-old baby, you know, or a three-hour-old baby, and then four more times when that baby is not going to be even subject to it for 16 years?” he asked Rogan. Kennedy’s story sounds informed: He is facile with epidemiology and vaccine regulations; he can describe historical machinations that supposedly took place between Merck and the CDC. But the truth is that most chronic hepatitis B infections are contracted during early childhood, or through mother-to-child transmission. That’s why the World Health Organization recommends immunizing babies, and it’s why nearly every country has chosen to do so.

Kennedy does, at times, say true things about vaccines. He was not wrong, for example, when he told the podcaster Lex Fridman that early batches of the polio vaccine were contaminated with a virus called SV40. But he magnifies and distorts such flaws to the point of absurdity. SV40-containing vaccines did not cause an “explosion” of cancers, as he has argued. Kennedy is also right to say the MMR vaccine doesn’t always provide lifelong immunity to the mumps virus. However, his more extreme assertions—that the shot is causing mumps outbreaks in the military or that the disease is harmless in children—are wrong. (Before vaccination, service members routinely suffered from infections, and kids were at a heightened risk of developing brain inflammation and hearing loss.) Kennedy relies on scraps of truth to construct an alternative reality in which vaccines don’t work, their harms outweigh their benefits, and the diseases themselves aren’t so bad.

At his confirmation hearing, senators will ask him to defend that dangerous, alternative reality. He is likely to do so with impressive-sounding falsehoods, delivered with aplomb. Heed his own advice. No one should trust his word on this.

For more than 60 years, vaccination in the United States has been largely shaped by an obscure committee tasked with advising the federal government. In almost every case, the nation’s leaders have accepted in full the group’s advice on who should get vaccines and when. Experts I asked could recall only two exceptions. Following 9/11, the Bush administration expanded the group who’d be given smallpox vaccinations in preparation for the possibility of a bioterrorism attack, and at the height of the coronavirus pandemic, in 2021, the Biden administration added high-risk workers to the groups urged to receive a booster shot. Otherwise, what the Advisory Committee on Immunization Practices (ACIP) has recommended has effectively become the country’s unified vaccination policy.

This might soon change. Robert F. Kennedy Jr., one of the nation’s most prominent anti-vaccine activists and the likely next secretary of Health and Human Services, has said that he would not “take away” any vaccines. But Kennedy, if confirmed, would have the power to entirely remake ACIP, and he has made clear that he wants to reshape how America approaches immunity. Gregory Poland, the president of the Atria Academy of Science and Medicine and a former ACIP member, told me that if he were out to do just that, one of the first things he’d do is “get rid of or substantially change” the committee.

Over the years, the anti-vaccine movement has vehemently criticized ACIP’s recommendations and accused its members of conflicts of interest. NBC News has reported that, in a 2017 address, Kennedy himself said, “The people who are on ACIP are not public-health advocates … They work for the vaccine industry.” Kennedy has not publicly laid out explicit plans to reshuffle the makeup or charter of ACIP, and his press team did not return a request for comment. But should he repopulate ACIP with members whose views hew closer to his own, those alterations will be a bellwether for this country’s future preparedness—or lack thereof—against the world’s greatest infectious threats.

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Before ACIP existed, the task of urging the public to get vaccinated was largely left to professional organizations, such as the American Academy of Pediatrics, or ad hoc groups that evaluated one immunization at a time. By the 1960s, though, so many new vaccines had become available that the federal government saw the benefit of establishing a permanent advisory group. Today, the committee includes up to 19 voting members who are experts drawn from fields such as vaccinology, pediatrics, virology, and public health, serving four-year terms. The CDC solicits nominations for new members, but the HHS secretary, who oversees the CDC and numerous other health-related agencies, ultimately selects the committee; the secretary can also remove members at their discretion. The committee “is intended to be a scientific body, not a political body,” Grace Lee, who chaired ACIP through the end of 2023, told me. ACIP’s charter explicitly states that committee members cannot be employed by vaccine manufacturers, and must disclose real and perceived conflicts of interest.

HHS Secretaries typically do not meddle extensively with ACIP membership or its necessarily nerdy deliberations, Jason Schwartz, a vaccine-policy expert at Yale, told me. The committee’s job is to rigorously evaluate vaccine performance and safety, in public view, then use that information to help the CDC make recommendations for how those immunizations should be used. Functionally, that means meeting for hours at a time to pore over bar graphs and pie charts and debate the minutiae of immunization efficacy. Those decisions, though, have major implications for the country’s defense against disease. ACIP is the primary reason the United States has, since the 1990s, had an immunization schedule that physicians across the country treat as a playbook for maintaining the health of both adults and kids, and that states use to guide school vaccine mandates.

The committee’s decisions have, over the years, turned the tide against a slew of diseases. ACIP steered the U.S. toward giving a second dose of the MMR vaccine to children before elementary school, rather than delaying it until early adolescence, in order to optimally protect kids from a trifecta of debilitating viruses. (Measles was declared eliminated in the U.S. in 2000.) The committee spurred the CDC’s recommendation for a Tdap booster during the third trimester of pregnancy, which has guarded newborn babies against whooping cough. It pushed the country to switch to an inactivated polio vaccine at the turn of the millennium, helping to prevent the virus from reestablishing itself in the country.

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I reached out to both current ACIP members and the Department of Health and Human Services to ask about Kenndy’s pending influence over the committee. ACIP Chair Helen K. Talbot and other current ACIP members emphasized the group’s importance to keeping the U.S. vaccinated, but declined to comment about politically motivated changes to its membership. The Department of Health and Human Services did not return a request for comment.

Should ACIP end up stacked with experts whose views mirror Kennedy’s, “it’s hard not to imagine our vaccination schedules looking different over the next few years,” Schwartz told me. Altered recommendations might make health-care providers more willing to administer shots to children on a delayed schedule, or hesitate to offer certain shots to families at all. Changes to ACIP could also have consequences for vaccine availability. Pharmaceutical companies might be less motivated to manufacture new shots for diseases that jurisdictions or health-care providers are no longer as eager to vaccinate against. Children on Medicaid receive free vaccines based on an ACIP-generated list, and taking a particular shot off that roster might mean that those kids will no longer receive that immunization at all.

At one extreme, the new administration could, in theory, simply disband the committee altogether, Schwartz told me, and have the government unilaterally lay down the country’s vaccination policies. At another, the CDC director, who has never been beholden to the committee’s advice, could begin ignoring it more often. (Trump’s choice to lead the CDC, the physician and former Florida congressman Dave Weldon, has been a critic of the agency and its vaccine program.) Most likely, though, the nation’s new health leaders will choose to reshape the committee into one whose viewpoints would seem to legitimize their own. The effects of these choices might not be obvious at first, but a committee that has less academic expertise, spends less time digging into scientific data, and is less inclined to recommend any vaccines could, over time, erode America’s defenses—inviting more disease, and more death, all of it preventable.