Kennedy knows, as he wrote in that same op-ed, that what actually prevents measles is a vaccine. Yet Kennedy, in discussing the fatal measles outbreak in West Texas, has been quick to de-emphasize that fact, instead telling Fox News that health officials in Texas “are getting very, very good results” with patients by using cod liver oil, which he said had high concentrations of vitamin A and vitamin D, along with an antibiotic called clarithromycin and a steroid, budesonide.

The secretary and longtime vaccine skeptic was referring to people who’d already become sick with the deadly virus—not as a prevention measure. But his word choice could easily confuse that issue, experts say. And at a time when exactitude feels crucial, with a second death in the growing U.S. outbreak reported Thursday, that is a point of tremendous concern. 

“I think what he’s doing as Secretary of Health and Human Services, as the head of the nation’s largest public health agency, is misleading the public about vaccines and about treatments for measles at a time when there’s a measles outbreak,” says Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia.

“With measles, there’s a way to prevent it: vaccines,” Offit says. “It would be nice if [Kennedy] was clear and definitive and straightforward that vaccines were the single best way to prevent measles.”

The World Health Organization recommends two doses of vitamin A for all children or adults with measles, as the infection itself can deplete vitamin A stores in the body. But that recommendation is for those already infected with the virus; the vitamin does not prevent infection in the first place.

“There is a concerning amount of incorrect information about measles circulating on social media, especially regarding vitamin A,” says Lesley Motheral, an associate professor of pediatrics at the Texas Tech University Health Sciences Center. “Due to the misinformation, we are concerned that parents will go to the store and purchase vitamin A to give to their children for prophylaxis. Vitamin A does not prevent measles.”

Community immunity vs. personal choice

In the op-ed, Kennedy noted that vaccines protect individual children from measles and contribute to community immunity. But rather than emphatically encouraging vaccination and touting their effectiveness, he added that the decision to vaccinate “is a personal one.” Kennedy also wrote that improvements in sanitation and nutrition had eliminated 98% of measles deaths prior to the vaccine’s development. While there is some evidence for that, Kennedy failed to share that to the federal Centers for Disease Control and Prevention, “widespread use of measles vaccine drastically reduced the disease rates in the 20th century.”

“It’s interesting in that he started off by talking about the importance of community immunity, and then proceeded to talk about how it’s your personal choice,” Offit says. 

According to the CDC’s Feb. 28 update, the vast majority of the 164 total documented measles cases in the U.S. so far this year were unvaccinated. The science on the measles, mumps and rubella (MMR) vaccine, meanwhile, is astoundingly clear: the CDC says a single MMR dose is 93% effective against measles, and two doses—the recommended course—are 97% effective.

“There should be a ringing affirmation that every child, unless they have genuine medical contraindications, should be vaccinated against measles,” says William Schaffner, past medical director of the National Foundation for Infectious Diseases. “I could not say that more strongly.”

Instead, Kennedy has only halfheartedly endorsed vaccination, while effusively discussing post-infection treatments. Even then, experts say, the secretary’s claims are either in desperate need of context or plain wrong.

Studies have shown, they say, that in the developing world where children who contract measles are often undernourished, giving them doses of vitamin A can prevent the more severe aspects of the disease and save lives. “But there’s no clear evidence that’s true in the United States,” says Offit, in large measure because there haven’t been enough cases of measles to warrant such a study.

In the U.S., the CDC calls vaccination “the best defense” against becoming infected with measles. A new update offers vitamin A as potential supportive care for an already-infected infant or child. The National Institutes of Health notes that taking too much supplemental vitamin A can result in blurred vision, dizziness and liver damage, among other things.

Moreover, “there are a number of studies showing it to be of marginal benefit or not much benefit against measles, and it’s certainly not a substitute for vaccination,” says vaccine scientist and pediatrician Peter Hotez.

“The most important thing that people need to understand is that measles is a virus,” says Tina Tan, president of the Infectious Diseases Society of America and a professor of pediatrics at Northwestern University. “There are no antivirals that are licensed for treatment of measles.”

That includes antibiotics like clarithromycin and the steroid budesonide, about which Tan says there is “zero (scientific) evidence” of effectiveness against measles but plenty of potential risk. “They’re just pulling things out of the air and saying this and that,” Tan says.

Upheaval in public health

Since Kennedy took office three weeks ago: two key vaccine advisory committee meetings were canceled; a large, multimillion-dollar government-funded study with Vaxart to test its oral COVID pill vaccine was halted, a company spokesperson confirmed to Fortune; Kennedy announced that he planned to review the childhood vaccine schedule; the CDC was ordered reportedly to halt its “Wild to Mild” publicity campaign that promoted the flu shot; and in the midst of a bird flu outbreak, U.S. health officials are reevaluating a $590 million contract that the Biden administration made with Moderna Inc. to help develop an mRNA-based bird flu vaccine, per Bloomberg.

The experts aren’t alone in their concern. On March 3, U.S. Sen. Elizabeth Warren (D-Mass.), who loudly opposed Kennedy’s confirmation at HHS, sent Kennedy a letter demanding that he clarify his “intentions regarding vaccine policy,” CNN reported.

“These are dangerous times for public health,” Warren wrote, according to the news agency. “Your irresponsible and reckless efforts to undermine the nation’s vaccine policy threaten to fan the flames of disaster.”

The Texas measles outbreak, which has already claimed the life of an unvaccinated six year-old child, provides a dark working example of the concerns around Kennedy. As of March 4, the Texas Department of State Health Services had recorded 159 cases of the virus since late January, a total that health officials say is probably an undercount because of the remote and historically under-unvaccinated Mennonite community area in Gaines County where the majority of the cases have been identified.

The second death, announced Thursday, involved a New Mexico adult who lived just across the state border from Gaines County, Texas. Though the cause of death is under investigation, the New Mexico Department of Health said the person, who was unvaccinated, had tested positive for measles. The person did not seek medical care before passing.

Researchers, virologists and other experts say they’re concerned that Kennedy’s tenure at HHS will bear similar characteristics similar to those he has put on display in addressing the growing measles problem. Repeatedly tested and proven science may well be shunned in favor of an anti-vax ideology—and public health could suffer tremendously as a result.

‘This is going to be long-term’

This is all coming at a time when the nation can ill-afford another outbreak. Virologists are already tracking the bird flu virus, about which they worry that combinations with seasonal flu may bring it closer to widespread human infection. The flu season itself is the most intense in more than a decade in the U.S., according to CDC data.

Though measles cases have been reported in nine states, West Texas is home to the overwhelming majority of them. With an undercount likely in part because the Mennonite community generally avoids traditional health care services, the outbreak may well be—and become—more severe than so far documented.

Read more from Fortune

“I think it’s going to be months (before control is established), when you look at other writeups about other outbreaks,” says Katherine Wells, director of public health in Lubbock, about 75 miles from the epicenter. “I’m prepping my staff that this is not just a couple of days. This is going to be long-term, working on this.”

Wells says she and her staff will be advocating for residents to become vaccinated if they’re not already, adding, “I would like to remind people that we’ve been giving this MMR vaccine for over 50 years.” But even the first recorded death from the virus in a decade, that of the child in West Texas, has not spurred Kennedy to make a clear-cut recommendation on vaccination.

Perhaps the closest he came was in his op-ed, where he wrote that vaccines need to be “readily accessible for all those who want them.” His department, which along with the CDC did not respond to a series of questions from Fortune, although the CDC confirmed the New Mexico case. The HHS is sending 2,000 doses of the measles vaccine to Texas health officials, delivering vitamin A and promising “comprehensive support” of their efforts on the ground.

Every dose may well be needed. The consequences of not having a highly vaccinated population against measles?

“You’re seeing it. This is what happens,” Offit says. “The last child death from measles in this country was in 2003. That was 22 years ago.” 

Now the child’s death isn’t even the most recent in the country to be associated with an outbreak that Offit and others say cries out for an unambiguous pro-vaccine message. They won’t get it.