Hiltzik: The myth of 'placebo' testing

Business Columnist

May 8, 2025 3 AM PT

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Americans have become woefully familiar with Health and Human Services Secretary Robert F. Kennedy Jr., the purveyor of flagrant misinformation about medical treatments. And with Robert F. Kennedy Jr., the minimizer of health crises such as the spreading measles outbreak. And with Robert F. Kennedy Jr., the antivaccine crusader.

Now let’s meet Robert F. Kennedy Jr., the promoter of a costly, time-consuming and distinctly unethical order for testing vaccines. “All new vaccines will undergo safety testing in placebo-controlled trials prior to licensure — a radical departure from past practices,” HHS announced in a May 1 statement. What it didn’t say was that the “departure” is “radical” because it’s shunned by medical authorities as a bad thing.

Just this week, Kennedy’s agency doubled down on this order with the appointment of Vinay Prasad, an oncologist at UC San Francisco, as head of the Center for Biologics Evaluation and Research, the division at the Food and Drug Administration that oversees vaccine testing.

I suspect that none of the parents who volunteered for Jonas Salk’s polio vaccine trial were hoping their children were in the placebo group.

— Vaccine expert Paul Offit, referring to the nationwide clinical trial of the polio vaccine in 1954

Prasad was a strident critic of the Biden administration’s approach to the COVID-19 pandemic, including the COVID vaccines. In a blog post in late April, he called for clinical testing of COVID boosters, along the lines of Kennedy’s order. Prasad succeeds Peter Marks, a widely respected expert who resigned from the FDA in March after clashing with Kennedy.

“I was willing to work to address [Kennedy’s] concerns regarding vaccine safety and transparency,” Marks wrote in his resignation letter. “However, it has become clear that truth and transparency are not desired by the Secretary, but rather he wishes subservient confirmation of his misinformation and lies.”

The HHS announcement about Kennedy’s demand for placebo-controlled trials was unclear about how it defined “new vaccines.” But his prior claims about vaccine safety have made clear that he’s referring not only to first-generation vaccines for diseases, but also boosters and expanded formulations. That’s an important point, as I’ll cover in a moment.

The antivaccine camp, of which Kennedy has long been a leader, has pushed the claim that most childhood vaccines haven’t been adequately tested for safety because they haven’t been subjected to placebo-controlled trials — and therefore they may be unsafe.

“Except for the COVID vaccine, none of the vaccines on the CDC’s childhood recommended schedule was tested against an inert placebo, meaning we know very little about the actual risk profiles of these products,” Kennedy’s spokesman at HHS, Andrew Nixon, asserted in connection with the order.

Both components of that claim are misrepresentations.

Let’s take a closer look, starting with some rudimentary points.

The testing that Kennedy and Prasad advocate are randomized control trials. They’re correct in asserting that so-called RCTs are the gold standard in clinical testing of drugs and vaccines.

RCTs typically involve at least two groups of subjects: One receives the medicine in question and another — a control group — receives something else, such as a placebo, a concoction that’s designed to resemble the medicine but is essentially inert, with no evident effect on the disease. The placebo may be an injectable saline solution, or water, or a sugar pill.

And Kennedy, like other antivaxxers, is deceptive in saying that the safety of vaccines should be questioned if it hasn’t been tested against an “inert placebo.”

That brings us to the ethics of clinical testing, and why Kennedy’s policy is so dangerous.

Testing a vaccine against a true placebo is ethical and proper when it’s the first treatment for a disease for which no other safe and effective treatment exists. That’s not the case, however, when a known treatment does exist — say after a vaccine has been shown to be safe and effective and has become the standard of care.

As vaccine specialist Paul Offit of Children’s Hospital of Philadelphia has explained, subjecting new versions of those vaccines to placebo-controlled testing — giving some subjects the new vaccine and the control subjects no treatment, would be unethical, because it would require depriving the placebo group access to a known treatment. That was the conclusion of an expert panel assembled by the World Health Organization in 2014.

Offit, in a 2023 rejoinder to Kennedy’s appearance on a Joe Rogan podcast, in which he claimed that drug companies “never do placebo-controlled trials,” pointed to what may be the most famous vaccine trial to illustrate this point.

That was the nationwide trial of Jonas Salk’s polio vaccine. In 1954, 420,000 first- and second-graders were given the Salk shot, and 200,000 got a shot of salt water. Salk objected to the trial’s design. Smaller trials had established the safety and efficacy of his vaccine, so the plan meant depriving 200,000 children of immunity to a disease that was paralyzing 50,000 children a year and killing 1,500.

As Offit noted, in the full trial 16 children died from polio; all were in the placebo group. So were 34 of the 36 children paralyzed in the course of the trial. “These are the gentle heroes we leave behind,” Offit wrote.

Now let’s examine Kennedy’s order as it applies to modern vaccines. As the veteran pseudoscience debunker David Gorski has pointed out, contrary to the assertion by Kennedy’s spokesman, almost none of the vaccines on the current childhood vaccination list is a first-generation vaccine warranting placebo testing. (An exception is Gardasil, which safeguards against human papilloma virus.) They’re upgraded preparations of vaccines that themselves underwent placebo-controlled trials, or formulations aimed at new variants of the targeted disease, or shots that inoculate against several diseases all at once.

To demand that every new formulation be tested against an inert placebo would mean turning back the clock to reproduce trials that may have taken place decades ago, but resulted in the licensing of the original vaccine after safety and efficacy were established.

That means it would have been unethical to test the new version against a saline control, because the control group would be deprived of any effective treatment. “The bottom line,” Gorski writes, “is that, if you trace back the history of the vaccines developed for a disease like, say, measles, you will eventually find the RCT testing the first effective vaccine against it and that vaccine will have had a placebo control.”

He’s right. In a tweet thread, vaccinologist Peter Hotez traced back the history of several vaccines to their initial RCTs.

What makes Kennedy’s order especially cynical is that designing and implementing a clinical trial is an extraordinarily complex, costly and time-consuming process. As a team of Canadian researchers observed in a 2018 Nature article, a full-scale Phase 3 clinical trial — the level at which drugs and vaccines are studied for safety, efficacy and dosing — requires as many as 3,000 participants and can take as long as four years.

In an online posting last month, Prasad ridiculed “the mainstream media” for being upset about the idea that COVID boosters should in effect receive full randomized clinical trials before approval. He took particular issue with an article by Helen Braswell of STAT asserting that such a requirement might well delay approval of a vaccine targeting a new COVID variant until it was too late to protect users from that variant. Prasad called the argument false, because “the virus spreads year round.”

Is that so? At the height of the pandemic, new COVID variants sometimes appeared within months of one another. The virulent Delta variant, for example, appeared in the spring of 2021 and was overtaken by the Omicron variant, which also caused severe disease, that November.

Delays in rolling out vaccines to combat newly emergent disease strains and variants could cost millions of lives. Under existing vaccine approval protocols, the COVID vaccines prevented as many as 20 million deaths globally within a year after they were introduced early in 2021.

Prasad’s new job will put him in charge of developing vaccine testing policies and overseeing the design and approval of clinical trials. I asked him via email what policies he would pursue, whether he was in alignment with Kennedy’s approach, and how he expected vaccine developers to reconcile the costs and time constraints of undertaking clinical trials on the scale he advocates with the imperatives of public health. I didn’t receive a reply.

So far, the Kennedy regime at HHS has lived down to the worst expectations of his critics. His devotion to unnecessary testing of vaccines that have already shown their safety and efficacy is only one aspect of a comprehensive assault on public confidence in science-based medicine.

In a recent appearance on Sean Hannity’s Fox News program, Kennedy dismissed the severity of the current measles outbreak and denigrated the effectiveness of the measles vaccine. The current outbreak of 935 cases is by far the worst in the U.S. since 2019, when 1,274 cases were recorded; at the current rate, we are on the path to nearly 3,000 this year.

Kennedy has promoted almost useless nostrums against measles, such as Vitamin A, while describing vaccination as a personal choice. That’s devastatingly wrongheaded. Kennedy confuses “medicine” and “public health.” The former concerns itself with the individual; the latter with the community. Vaccine policy belongs in the latter category because vaccines are most effective when the effort is communitywide.

Measles is among the most contagious diseases known to humankind, which means that communal vaccination is crucial. Professionals have concluded that a 95% vaccination rate is the minimum required to protect the most vulnerable, such as infants, from infection; as of 2024, the U.S. vaccination rate among kindergartners had fallen from 95.2% in 2019-20 to 92.7%.

The Centers for Disease Control and Prevention, which falls within Kennedy’s jurisdiction, says the decline in measles vaccinations leaves 280,000 kindergartners at risk. Two children in the U.S. already have died from a disease that was thought to have been eradicated in the U.S. in 2020; Kennedy doesn’t seem concerned that the toll on his watch is poised to get much worse.