Across marathon hearings before lawmakers over the past week, health secretary Robert F Kennedy Jr was repeatedly challenged over his response to the measles outbreak — and he repeatedly refused to take responsibility for the rising number of infections. But the scale of the surge and Kennedy’s own role in undermining vaccines make that deflection hard to swallow.

US measles cases hit a nearly 35-year high in 2025, Kennedy’s first year leading the nation’s top health agency, with the CDC recording nearly 2,300 infections and three deaths. The disease has spread even faster this year, with 19 new outbreaks and nearly 1,750 cases by mid-April. That includes almost 100 hospital admissions — more than half of them children. All for a disease the US thought it vanquished in 2000.

Kennedy, who has reportedly faced pressure to tone down his anti-vaccine rhetoric, says this backsliding isn’t his fault. Throughout the seven separate hearings in the House and Senate, he leant into a reasonable-sounding defence: measles was already spreading when he took office, so he can’t be blamed for the current situation.

That argument ignores the years Kennedy spent stoking fears about the safety of vaccines (a campaign that had been particularly focused on the measles, mumps and rubella shot). It might be more convincing if he hadn’t stopped short of a full-throated endorsement of vaccination when the first outbreak began in West Texas. Or if he hadn’t systematically dismantled the public health systems that ensure Americans have access to vaccines. Or if he hadn’t continued to challenge the decades of science showing that vaccines save lives at the hearing itself.

None of those are the actions of someone who wants to end an outbreak with the best tool available: vaccination.

The consequences are becoming clear: The US is now on the brink of losing its measles elimination status, which a country is granted by global health authorities when it doesn’t have large outbreaks or sustained spread for a year. That determination won’t be made until November, but the CDC recently made public a trove of genomic data from measles samples collected as the virus spread last year. That will let scientists understand how many cases stem from community transmission.

Kennedy’s replies throughout the hearings seemed to downplay the seriousness of the situation. Public health experts disagree.

“I would not underestimate how important losing that status is,” says Adam Ratner, a member of the American Academy of Paediatrics’ infectious diseases committee, and author of the book Booster Shots: The Urgent Lessons of Measles and the Uncertain Future of Children's Health. The designation might seem like semantics, he says, but getting to that status was a 40-year journey that involved an incredible amount of work.

That began in earnest in the 1980s and 1990s, when major outbreaks prompted states to put in place school vaccine mandates and the federal government in 1994 introduced the hugely successful Vaccines for Children Programme, which has since provided hundreds of millions of free shots to millions of eligible children.

Those initiatives, alongside a gargantuan effort by federal, state and local public health officials, allowed the US to quickly tamp down any new cases before they became a problem. By 2000, the US had achieved measles elimination status.

Recreating that success feels downright impossible under Kennedy’s leadership.

“I think it is going to be an uphill battle,” Ratner says.

Childhood vaccination rates have fallen since the pandemic, with just 92.5 per cent of kindergarteners starting school in 2024 up-to-date on their MMR shot — a figure that had dropped below 90 per cent in almost a third of states. The goal is to maintain levels of 95 per cent or better to achieve herd immunity.

In the past, measles outbreaks have helped reverse declines in vaccination rates. After the infamous Disneyland measles outbreak in California that began in late 2014, vaccination rates among kindergarteners increased by 20 to 30 per cent in schools where uptake had lagged the most, according to a New York Times analysis.

Yet that improvement wasn’t all because of personal awakenings about the benefits of vaccines or fears over the virus, but rather came from a change in policy. In 2016, California changed its previously lax law to a stricter one that closed loopholes and exemptions.

Today, though, too many states, emboldened by Kennedy’s anti-vaccine views, are going in the opposite direction: They are introducing laws that make it easier for parents to refuse vaccinations for their children.

Despite those trends, there are small but encouraging signs of change in states where measles has circulated. Bloomberg recently reported that the views of some previously hesitant or even anti-vaccine parents were beginning to shift amid the current outbreak.

The preventable deaths of two children and terrifying cases of brain swelling among infected children certainly should strike fear in any parent’s heart. Whether that’s enough to counteract the broader messaging from the top echelons of government remains to be seen. If the US is eventually able to turn around vaccination rates and snuff out these outbreaks, one thing is certain: it will be in spite of Kennedy’s leadership, not because of it.

• Lisa Jarvis is a Bloomberg Opinion columnist covering biotech, healthcare and the pharmaceutical industry