There is historical precedent for how Robert F. Kennedy Jr is handling his ascension to high office. It’s an episode that did not end well.

Thabo Mbeki, who succeeded Nelson Mandela as President of South Africa and ruled in his shadow for nine years, was the world’s most powerful Aids denier. As president, he could do far more than spout long-debunked theories about HIV not causing Aids. He appointed a health minister who insisted that the cure was garlic, lemons, beets and beer. And he forbade public hospitals to provide the antiviral drugs that were saving lives in other African countries.

Both Mbeki and his people paid a price. In 2008, he was ousted in a party power struggle — after his intransigence had killed an estimated 365,000 South Africans, including 35,000 newborns who might have lived if their HIV-positive mothers had been given just a few doses of a drug to prevent mother-child transmission, according to a Harvard study.

In 2000, when doctors accused Mbeki of spreading falsehoods and promoting quack cures, he created a panel to “look at the cause of Aids” and staffed it with well-known Aids denialists. Kennedy, who is facing similar accusations, has commissioned a study on whether vaccines cause autism and has, according to The Washington Post, hired a notorious vaccine sceptic, David Geier, to run it. Geier, who is not a doctor, and his father co-authored papers claiming that vaccines cause autism. They also worked together at a Maryland clinic that treated autistic children with Lupron, a drug used for the chemical castration of rapists. In 2012, Geier’s father lost his medical licence for prescribing the treatment and Geier was fined $10,000 for practising medicine without a licence.

These actions demonstrate how stubbornly both Mbeki and Kennedy have refused to accept clear evidence that their beliefs are wrong.

When the Aids epidemic began in 1981, it was a mysterious disease that seemed to kill only gay men. Its name initially was not Aids but Grid — gay-related immune deficiency. While the disease’s cause was unknown, there was speculation that the “gay lifestyle” — exhausting disco dancing, multiple sex partners and the use of amyl nitrate poppers — might somehow be to blame. Science writers initially reported this as a theory to be investigated, although many experts were sceptical. But as it became clearer that Aids led to the deaths of haemophiliacs, heroin users and blood-transfusion recipients, and when it was shown to be widespread in Haiti and central Africa, it became obvious that it was probably a blood-borne virus like hepatitis.

In 1983, HIV itself was discovered. When it turned out to be related to a virus that also killed chimpanzees, the denialists invented new theories, first blaming it on the “African lifestyle”, which relied on the racist stereotype that all Africans were malnourished, had malaria and drank polluted water. Then they claimed the antiretroviral drugs, rather than the virus, was killing Aids patients.

But by the time Mbeki created his panel, it had been clear for 17 years that HIV causes Aids. He tried desperately to silence his critics, and the confusion created by the denialists on his panel scared some Africans away from effective drugs. Today, Kennedy is following the same playbook, raising doubts about the measles vaccine and promoting quack treatments such as vitamin A, cod-liver oil, budesonide and clarithromycin. Some children in Texas have now been admitted to hospital for liver damage caused by vitamin A overdoses.

As with Aids, the surge in autism that began in the late 1980s was a mystery. Its cause is still unknown, although scientists think it is related to older parents, survival of more premature infants and broader diagnoses of autism-spectrum disorders. Whether antidepressants might also play a role is being investigated.

In 1998, Andrew Wakefield, a gastroenterologist at a prominent London hospital, published a study in the Lancet, suggesting the measles vaccine might be to blame. Science writers treated his theory with respect in the beginning, even though it seemed biologically unlikely. When further studies contradicted Wakefield’s theories, he would dutifully call anti-vaccine groups such as SafeMinds for comment. But as the studies demonstrating that the measles vaccine does not cause autism piled up, antivaxers refused to accept them. Instead, they invented new theories — that a mercury preservative in vaccines was to blame or an aluminium booster or “vaccine overload”. Finally, in the wake of investigative journalism showing that Wakefield had been paid by lawyers suing vaccine makers, after the Lancet retracted the study and after Wakefield lost his medical licence, we no longer felt obligated to quote anti-vaccine activists any more than reporters who write about space travel feel the need to quote people who believe the Apollo moon landings were faked. The anti-vaccine movement was discredited.

Then President Donald Trump unwisely chose the country’s most famous antivaxer to be secretary of health and human services.

In his appearance before the Senate, Kennedy said several times, “If you show me data, I will be the first person to assure the American people … that they need to take those vaccines.” He said he would tell mothers that vaccines do not cause autism “if the data is there”.

The independent senator Bernie Sanders rebuked him, pointing out that, as the nominee to be health secretary, “your job was to have looked at those studies”.

Dozens of studies have found no connection between vaccines and autism; 27 of these are summarised here. The most convincing are from countries with massive national health registries, such as this 2002 Danish study looking at 537,303 children born in Denmark from 1991 to 1998. Autism rates among unvaccinated children were virtually identical to rates among vaccinated ones, the research found. (The same authors published a follow-up study in 2019 looking at 657,461 children born from 1999 to 2010 that got the same result.)

Another type of study done by scientists in San Francisco, Philadelphia, France, Italy and elsewhere had mental health professionals watch home movies of children taken before they were vaccinated. They were consistently able to spot signs of autism, such as less eye contact and weaker response to their names, long before parents could. Clearly, autism was present before these babies got their measles shots.

Other studies have compared identical twins with fraternal twins in cases in which one twin had autism and all children were on the same vaccine schedule. In the case of identical twins, there was a 90 per cent chance that the second twin also was on the spectrum, while fraternal twins were on it only about 10 per cent of the time. This strongly suggests that autism is a genetic condition, not a vaccine reaction. Other scientists have studied infants with older siblings who already had autism diagnosed, which puts them at higher risk of also having it; they found no difference in autism rates between vaccinated and unvaccinated younger siblings.

Kennedy knows perfectly well that these data exist. Like Mbeki, he chooses not to look. Not as many Americans will die as did in South Africa, of course, because measles is not Aids and most Americans are vaccinated against it. But any deaths of children are unnecessary and should weigh on Kennedy’s conscience — if the data shows he has one.

• Donald G. McNeil Jr, a former global health reporter for The New York Times, is the author of The Wisdom of Plagues