Polymarket and Kalshi Now Take Bets on Measles and FDA Decisions

By Grace Kim

Prediction markets now let users wager on whether the US will lose its measles-elimination status in 2025 — and no federal regulator is tasked with stopping them.

Polymarket and Kalshi have opened contracts on public health outcomes: FDA approval of a skin-cancer vaccine, CDC changes to vaccine recommendations, drug trial results, and how many measles cases the US will record in 2026. Kalshi began listing health-related predictions over the summer; Polymarket has now joined.

The push surfaced publicly on a construction fence next to an elementary school in Brooklyn. A sign with a blue star-spangled background read "VACCINES" in bold capitals — and, in smaller letters at the bottom, "Will any state end vaccine markets?" next to the Polymarket logo. Within a week, someone ripped off the bottom half. The sign now just says "Vaccines."

What can you actually bet on?

The health contracts cover concrete, checkable events:

• When the FDA will approve a skin-cancer vaccine
• Whether the CDC will change its vaccine recommendations
• Drug trial outcomes and approvals
• US measles case counts in 2026
• Whether the US loses its measles-elimination status this year
• When certain officials will leave health agencies
• Whether any state ends vaccine mandates

"I am not surprised," said Matthew Eisenberg, professor and chair of health policy and management at the Johns Hopkins Bloomberg School of Public Health. "Kalshi and Polymarket will list contracts on anything with a checkable outcome."

How do the markets escape gambling rules?

The mechanism is a regulatory loophole. The platforms position themselves as financial derivatives, not bets, which places them under federal commodities law and oversight by the Commodity Futures Trading Commission — not under state gambling regulation. Several states have sued the companies, alleging they function as gambling sites.

"Gambling right now is like the wild, wild west," said Lia Nower, professor and director of the Center for Gambling Studies at Rutgers University. "There's no federal regulatory body that's really prescribing any limits on any of this, or just minimum guidelines for states to follow – so anything's possible."

She called the products functionally "identical" to regulated gambling.

The structure creates conflicts critics say nobody has addressed. Advocates or lawmakers could bet on ending state vaccine mandates, then introduce legislation to make it happen — Nower said there don't appear to be laws against that. Predictions on FDA decisions and trial endpoints "create a payoff for anyone with nonpublic information," Eisenberg said — agency reviewers, trial investigators, legislative staff. The risk "isn't necessarily that a reviewer takes a bribe – it's that the market now rewards leaks." Trial participants could also change behavior to move outcomes, and drug companies could shift trial timing.

What did the companies say?

Polymarket did not respond to questions about consequences for public health or medicine. Kalshi declined to answer on the record, but spokesperson Dani Lever defended the program in a statement: "Kalshi's clinical trial markets are a pilot program aimed at a structural problem in drug development: the people who best know whether a trial will succeed are scattered, and their insight rarely reaches the public. Public markets avoid those barriers."

Who pays for the harm?

Problem gambling is itself a growing public health concern. Nower co-authored a new report showing more than half of people aged 13 to 27 gambled in the past year. Among those young gamblers, 39.5% showed some degree of gambling-related risk and 10.3% were high risk. Gambling, she said, disproportionately affects people who are younger, Black or Hispanic and lower-income.

Eisenberg's research on online sports betting found legalization is followed by measurable increases in treatment for depression and anxiety among young men. States have discussed protections — deposit limits, self-exclusion, advertising rules, treatment funding from betting taxes. "But the prediction markets sit outside all of that," he said, and very little of their revenue flows to states through taxes.

"In effect, these are gambling products that have exited the only regulatory system designed to limit gambling harm," Eisenberg said.

Nator-level action is stirring: New Jersey is moving to restrict the markets, citing consumer protection and insider-trading concerns. "People with inside information or control over an outcome could potentially profit from what they call 'event contracts,'" Nower said. But the federal government still has no dedicated gambling regulator, and no NIH research centers focus on gambling as they do for alcohol and drug abuse. "It's just unaddressed at the federal level," she said.

Eisenberg's forecast is blunt: "Gambling on everything, everywhere, with fewer and fewer consumer protections." Still, he cautioned against reading the health contracts as public sentiment — prices that small can be moved by a single trader, he said, and "a few-hundred-dollar contract on the childhood vaccine schedule is not a forecast of anything."

Brooklyn already delivered its own verdict: the Polymarket half of that fence sign is gone.