Brian Deer is a journalist who recently published a book about anti-vaccine activists. In an opinion piece in the New York Times, he described how very dangerous Robert F. Kennedy is. If he should be confirmed as leader of the department of Health and Human Services, Deer predicts, he will surround himself with other quacks and vaccine deniers. Recently, he writes, Kennedy has been trying to obscure his radical views against vaccines by talking about food safety. Don’t be fooled. He does not trust science, and his stance on vaccines is dangerous.

He writes:

In November 2019, when an epidemic of measles was killing children and babies in Samoa, Robert F. Kennedy Jr. — who in recent days became Donald Trump’s pick to lead the department of Health and Human Services — sent the prime minister of Samoa a four-page letter. In it, he suggested the measles vaccine itself may have caused the outbreak.

He claimed that the vaccine might have “failed to produce antibodies” in vaccinated mothers sufficient to provide infants with immunity, that it perhaps provoked “the evolution of more virulent measles strains” and that children who received the vaccine may have inadvertently spread the virus to other children. “Please do not hesitate to contact me if I can be of any assistance,” he added, writing in his role as the chairman of Children’s Health Defense, an anti-vaccine group.

At the time of his letter, 16 people, many of them younger than 2, were already reported dead. Measles, which is among the most contagious diseases, can sometimes lead to brain swelling, pneumonia and death. For months, families grieved over heartbreaking little coffins, until a door-to-door vaccination campaign brought the calamity to a close. The final number of fatalities topped 80.

I was in Samoa during that outbreak as part of my more than 16 years of reporting on the anti-vaccine movement. The cause of the outbreak was not the vaccine, but most likely an infected traveler who brought the virus from New Zealand, which that year had had the biggest measles outbreaks in decades, especially among that country’s Indigenous and Pacific Islander communities. Migration and poverty were likely factors in a sudden spread of measles in Samoa and New Zealand. But, as an editorial in The New Zealand Medical Journal reported, so too was a factor that Mr. Kennedy specializes in: “increasing circulation of misinformation leading to distrust and reduced vaccination uptake.” Samoa’s vaccination rates had fallen to fewer than a third of eligible 1-year-olds.

Vaccine skepticism has ballooned worldwide, and Mr. Kennedy and others who back him have encouraged it. Americans may be well aware that their possible future health leader holds dangerous beliefs about vaccines. The consequences of his views — and those of his orbit — are not merely absurd but tragic.

In my reporting, parents have mentioned fearing vaccines after watching “Vaxxed,” a 90-minute documentary, which had also toured countries such as New Zealand. The film, focused on unproven allegations, was released more than three years before the Samoa measles outbreak. Among much else, it claimed the Centers for Disease Control and Prevention had committed fraud.

Two of the filmmakers — Del Bigtree and Andrew Wakefield — are buddies of Mr. Kennedy. The director, Mr. Wakefield, is a former doctor whose medical license was revoked in his native Britain in 2010 amid charges of ethical violations. One of the producers, Mr. Bigtree, became Mr. Kennedy’s presidential campaign communications chief.

In the years before the documentary was released, I revealed, in a series of articles, evidence that Mr. Wakefield’s research in the 1990s had been rigged at a London hospital to make it look as if the measles-mumps-rubella vaccine was linked to autism. This research was retracted in 2010. Mr. Kennedy certainly didn’t seem fazed by Mr. Wakefield’s professional downfall. “In any just society, we would be building statues to Andy Wakefield,” he yelled, for instance, from a platform he and Mr. Wakefield shared at an event in Washington, D.C., a few days before he sent his letter to Samoa.

Reports say Mr. Kennedy is reviewing résumés for his possible Health and Human Services Department empire. He’s reportedlyeyeing Dr. Joseph Ladapo, a Florida health official who has questioned the safety of Covid vaccines. I’d say Mr. Bigtree may get a role; Mr. Wakefield is trickier, given how discredited he is, even in the United States. But there are plenty of others in Mr. Kennedy’s circle whose claims ought to concern everyone.

Consider Sherri Tenpenny, a doctor who has been declared by Mr. Kennedy as “one of the great leaders” of the anti-vaccine movement. She has falsely claimed that a “metal” attached to a protein in the Covid shots was making their recipients magnetic. “They can put a key on their forehead and it sticks,” she told Ohio state lawmakers in June 2021. “They can put spoons and forks all over them and they can stick.” I could pluck plenty more outrageous characters from Mr. Kennedy’s circle over the years, including veteran AIDS denialists.

In recent days, Mr. Kennedy appears to have tried to change the conversation around his vaccine views to focus on America’s junk food diets. But his views on vaccines shouldn’t be forgotten. In January 2021, speaking to a gathering of loyalists in Ohio, he outlined a three-point checklist that had to be met for him to consider a Covid vaccine. First, he said, “you take one shot, you get lifetime immunity.” Second, side effects are only “one in a million.” Third, “herd immunity” is achieved at 70 percent public uptake — after which, he stipulated, “nobody in this society” ever gets the disease again.

“If they came up with that product,” he said, “I’d be happy to look at it.”

His audience laughed. But it’s not funny.