RFK Jr. pledged to fight Lyme disease. Does that include supporting a vaccine?

When the topic of Lyme disease comes up, Robert F. Kennedy Jr. often tells a story about standing in a bathtub in Westchester County, New York, in the 1980s, picking almost 30 ticks off of himself after a day in the woods.

He’s had the characteristic bullseye rash of Lyme disease and says all of his children have had the tickborne illness, two of them severely affected.

As secretary of the US Department of Health and Human Services, Kennedy has promised to take on Lyme disease, which is an even bigger problem now than it was 40 years ago. At a roundtable discussion he convened in December with patients, clinicians and researchers, he pledged greater support for improving diagnostics and treatment.

“We’ve got to figure out a way to make it safe for children to go back in the woods again,” Kennedy said.

Last week, a potential means of doing so emerged: Pfizer said it planned to file for regulatory approval of a Lyme disease vaccine that would be the first on the market in more than two decades.

But its path in the US could be rocky, not least because of Kennedy himself, who’s embraced both anti-vaccine views and conspiracy theories, including that Lyme disease may be a bioweapon engineered by US government scientists during the Cold War.

Beyond Kennedy, though, the US has a complicated history with Lyme disease vaccines, and some of those issues haven’t gone away.

The problem of Lyme disease is enormous – and getting worse.

About 476,000 people are estimated to be diagnosed with and treated for Lyme disease each year in the US, and the areas where it’s found have been expanding in almost every direction, helped by climate change and, possibly, changing land use.

“Lyme is entering areas where it didn’t occur before,” said Dr. Richard Ostfeld, a disease ecologist at the Cary Institute of Ecosystem Studies in Millbrook, New York.

The disease is caused by bacteria called Borrelia burgdorferi, and it’s spread to humans through blacklegged ticks. It can cause fever, fatigue and an oval or bullseye-like skin rash; without treatment, the infection can spread to the joints, heart and nervous system, causing arthritis, persistent pain and other problems.

Most cases caught early are treated effectively with antibiotics, but some patients have longer-lasting and sometimes devastating symptoms even after treatment, a condition referred to as post-treatment Lyme disease syndrome, or chronic or long Lyme.

And an increasing number of people are vulnerable as the ticks that carry Lyme-causing bacteria are on the move. Climate change is enabling them to spread into formerly colder climes, Ostfeld said, extending the warm periods of the year that allow them to seek hosts, which the ticks can’t do when the temperature is in the 30s or below.

But they’re also moving into warmer areas, including southward in the US, an expansion that may be driven by how we live.

“Suburbanization and the fragmentation of forests exacerbates Lyme disease risk,” Ostfeld said. And that has to do with mice and other rodents that carry Lyme-causing bacteria and are particularly choice hosts for blacklegged ticks, which then give the bacteria to us.

Those mice – white-footed mice in particular – “thrive in areas that are disturbed by people,” Ostfeld said.

Lyme’s toll was bad enough several decades ago that multiple pharmaceutical companies spent years and untold sums of money developing vaccines to try to prevent it. One, drugmaker GSK’s Lymerix, was successful in getting to market, approved by the US Food and Drug Administration in 1998.

But the odds were stacked against it from the beginning, with lukewarm endorsements from government bodies as it made its way through the regulatory process.

“The benefits are on the side of the vaccine in the short term,” Dr. Dixie Snider of the US Centers for Disease Control and Prevention is quoted as saying after an FDA advisory panel recommended its approval in May of 1998. “In the long term, we don’t know.”

The New York Times headlined its story on the approval in December of that year: “Lyme vaccine is approved, with caveat,” pointing out that the FDA “was unusually cautious in recommending use of the vaccine.”

The caveats included that the vaccine was tested only in people ages 15 to 70, so it wasn’t cleared for other age groups, and that it took a year and three doses to reach protection of about 75% against cases of Lyme disease, meaning people would still need to take precautions.

A tepid recommendation from the CDC’s vaccine advisers further sealed its fate, according to Dr. Paul Offit, then a member of that group, called the Advisory Committee on Immunization Practices.

“The ACIP really killed that product,” he said. “They damned it with faint praise.”

The committee, whose recommendations typically guide how vaccines are used in the US, recommended that for people who live, work or do recreational activities in areas of high or moderate risk for Lyme disease, vaccination “should be considered.”

It wasn’t a routine recommendation, a stronger endorsement that would have been more clear, Offit said. And he pointed out that a routine recommendation could have served another purpose: potentially providing a form of protection for the vaccine against litigation by including it in the Vaccine Injury Compensation Program.

That program was set up in the 1980s after lawsuits against vaccine manufacturers risked driving them out of the market and creating vaccine shortages; it provides a way to compensate people found to be injured by a vaccine in a no-fault alternative to the legal system.

Lymerix hadn’t shown any major safety concerns in its major clinical trial, which was run in 10,936 people. But after it got on the market, there were fears the vaccine might cause a symptom it was aiming to prevent.

“There was a lot of, turns out, erroneous publicity that the vaccine caused arthritis,” said Dr. Eugene Shapiro, a professor of pediatrics and epidemiology at the Yale School of Medicine.

Lawsuits piled up. Researchers reviewed data from a federal database of vaccine adverse event reports, finding that of 1.4 million doses of Lymerix that were distributed in its first 19 months on the market, there were 905 events reported, including 59 patients with arthritis.

It was a level well below what might be expected generally in the population, and an FDA advisory panel concluded in 2001 that there was no association between the vaccine and arthritis.

Nonetheless, interest in the vaccine petered out, and in early 2002, GSK pulled it from the market, citing “poor demand.” The company settled the lawsuits in 2003 for about $1 million.

A second vaccine against Lyme disease that had shown similar, even potentially stronger, results in clinical trials was never submitted for approval.

“It’s really a sad story,” vaccine pioneer Dr. Stanley Plotkin told CNN. “We had a good vaccine that failed because people didn’t use it.”

It’s not clear whether the new vaccine, from Pfizer and partner Valneva, will have an easier time.

The results they reported last week weren’t a clear win: The vaccine missed one statistical bar in its clinical trial but met another. Pfizer nonetheless said it was “confident in the vaccine’s potential and is planning submissions to regulatory authorities.”

The new vaccine takes a similar approach to Lymerix, delivering a surface protein found on Lyme bacteria so the body’s immune system generates antibodies against it. It doesn’t stop a tick from biting someone, but if the antibodies are present when the tick takes a blood meal, they can neutralize the bacteria in the tick’s gut, preventing infection.

Pfizer and Valneva’s results showed that four doses of the vaccine delivered over two seasons reduced cases of Lyme disease by about 75%, similar to the efficacy for Lymerix.

The vaccines have a few key differences: Although Lymerix provided protection against just one type of surface protein – the kind predominant in North America – the newer vaccine protects against the six most prevalent in North America and Europe.

And though the Lymerix vaccine wasn’t found to cause arthritis, the Pfizer and Valneva vaccine was designed to leave out the portion of the surface protein that raised that theoretical risk, Shapiro said. He noted that he received a small payment for participating in conferences about the Pfizer and Valneva vaccine, and he wasn’t involved with Lymerix.

Whether a Lyme disease vaccine would be embraced widely now – even as Lyme incidence has been shooting up – is “the big question,” said Dr. Linden Hu, co-director of the Tufts University Lyme Disease Initiative and a professor of immunology at Tufts Medical School.

“A four-dose vaccine with 75% efficacy might be a difficult sell,” Hu said, “but for those that are willing, it will be great to have a vaccine as an option for protection again.”

Some advocacy groups are unenthusiastic. Lorraine Johnson, chief executive officer of LymeDisease.org, noted that “the Lyme community had a sour taste in their mouth” from the experience with Lymerix, though she acknowledged it wasn’t proved that the vaccine caused arthritis.

“There were enough patients who became profoundly ill, and physicians were raising the alarm,” she said. “It was taken as a very, very serious threat by the Lyme community.”

Johnson also pointed out that the vaccine protects only against Lyme disease, not the number of other pathogens that can be transmitted by the same ticks, such as Powassan virus or the parasite that causes babesiosis.

“Why that matters is, a patient could get a vaccine that covers Lyme and then have a false sense of complacency that they’re covered if they get a tick bite, and they’re not covered because they’ve got the potential for these other tickborne infections,” she said.

The community, Johnson said, has been behind broader approaches. “You really want to have the ticks falling off of you.”

There are studies underway on attempts to accomplish just that, including a pill that aims to kill ticks after they bite, preventing them from spreading pathogens. Hu noted that his lab was involved in part of its testing, as well as separate work on vaccines for mice in the wild to try to cut down transmission. He also has worked with Moderna on its mRNA-based Lyme vaccine in development.

The tick-killing pill is in the works at biotech company Tarsus Pharmaceuticals, which said Tuesday that it has started a midstage clinical trial of it, with results early next year.

A key question for the path of a Lyme disease vaccine in the US is Kennedy himself, who as HHS secretary sits above the FDA and the CDC, pivotal agencies for any vaccine’s approval and uptake.

He’s promoted the conspiracy theory that Lyme disease was a bioweapon engineered at the Plum Island Animal Disease Center, a US government facility, a narrative that disease ecologist Ostfeld calls “destructive and clearly false.”

Ostfeld pointed to evidence suggesting that Lyme-causing bacteria “has existed in essentially its current-day form for hundreds of thousands of years,” and “the tick also has existed in largely its present form for millions of years.”

“The last thing that I would ever use for a bioweapon would be some kind of tickborne disease where the tick doesn’t even transmit the pathogen to its babies,” Ostfeld said. “The tick bites three times in its life and takes two years to do that. What could be less efficient, less operational, as a weapon than something like a tickborne bacterium that can be cleared from your system with antibiotics within a couple weeks?”

Plotkin put it another way: “Using the technical term, it was bullsh*t.”

Nonetheless, a directive for the Government Accountability Office to prepare a report on biological weapons experiments on ticks and tickborne diseases was included in the 2026 National Defense Authorization Act, signed into law by President Donald Trump in December.

It was championed by New Jersey Rep. Chris Smith, founder and co-chair of the Congressional Lyme and Tick-Borne Disease Caucus.

Smith said the aim of the amendment “is to generate insights into the origin, nature, and comorbidities associated with Lyme and other tick-borne pathogens,” which he said he believes will “generate better clinician awareness, diagnostics, treatments and, ultimately, a cure.”

He said he’s supported efforts for more than three decades to research and develop a vaccine, and he called Pfizer’s results “extremely promising.”

Kennedy has been less enthusiastic about Lyme vaccines in the past. In 2022, when Pfizer and Valneva released results from earlier-stage trials of their vaccine, Kennedy posted a story on social media from the anti-vaccine advocacy group he led, Children’s Health Defense, that posited “some experts say treatment is a better solution.”

Since taking the helm at HHS, he has overhauled both the childhood vaccine schedule and the CDC’s vaccine advisory committee – moves now in limbo after an order from a federal judge. His vaccines chief at the FDA is on his way out, and vaccine makers have said they’re pulling back on some development because of the environment under Kennedy.

And despite his advocacy for Lyme disease, Kennedy has not focused on vaccination as a solution.

Some of the only mentions of vaccines at the December HHS roundtable on Lyme disease came from invited lawmakers, including Sen. Susan Collins of Maine, who said, “One of the most important tools that I hope we’ll continue to research to combat Lyme disease is a vaccine.”

Collins, a Republican, made a similar statement in a question to Kennedy during his confirmation hearing last year, asking him what influence he’d exercise over new vaccine approvals, “such as one for Lyme disease,” as HHS secretary.

Kennedy pledged, “There is nobody who will fight harder to find a vaccine or a treatment for Lyme disease than me.”

Andrew Nixon, a spokesperson for HHS, told CNN that “HHS supports rigorous, gold-standard science to better understand, prevent, and treat Lyme disease.”

He didn’t respond to multiple questions about whether HHS’s support of prevention efforts extends to vaccines.