Polymarket and Kalshi List Bets on Measles and Drug Trials, Raising Insider-Information Questions

A Polymarket sign pasted on a construction fence beside an elementary school in Brooklyn asked, "Will any state end vaccine markets?" Within a week, someone tore off the bottom half, with the logo and the text inviting a prediction. The sign is a small episode, but it shows how public health questions are now being turned into tradeable contracts.

Kalshi began offering health predictions over the summer, and Polymarket has now joined it. Users can bet on when the US Food and Drug Administration will approve a skin-cancer vaccine, whether the Centers for Disease Control and Prevention will change its vaccine recommendations, how many measles cases the US will record in 2026, and whether it will lose its measles-elimination status this year. Kalshi also runs clinical trial markets, which it describes as a pilot.

The more pressing question is who can see the outcome before everyone else. Matthew Eisenberg of the Johns Hopkins Bloomberg School of Public Health argues that contracts on FDA decisions and trial endpoints "create a payoff for anyone with nonpublic information", such as agency reviewers, trial investigators and legislative staff. His point is that the risk is less a bribe than a market that rewards leaks. This is expert analysis, and the article does not document any case of misuse.

Kalshi's spokesperson, Dani Lever, said its trial markets address a problem in drug development, where people with the best knowledge of a trial's prospects are scattered and rarely share it publicly. Polymarket did not respond to questions about consequences for public health or medicine. Kalshi did not respond on the record to the same questions. Neither silence nor the company statement settles whether the markets improve transparency; the statement is Kalshi's own account of its purpose.

On regulation, Lia Nower of Rutgers University says the platforms present themselves as financial derivatives under federal commodities law, which places them under the Commodity Futures Trading Commission rather than state gambling regulators. Several states have sued, alleging they operate as gambling sites, and New Jersey is moving to restrict them. Those disputes are unresolved, and the platforms may contest them. Nower also said she knows of no law that stops officials from betting on policy outcomes they could later influence, which is her reading rather than a legal finding.

The cost of weak oversight falls on consumers as well as on research integrity. Nower co-authored a report finding that more than half of people aged 13 to 27 gambled in the past year. Eisenberg says prediction markets sit outside the consumer protections being debated for sports betting, such as deposit limits, self-exclusion and treatment funding from betting taxes. The link between these health contracts and gambling harm is an analytical concern; the article does not measure it.

Eisenberg also cautioned that a few-hundred-dollar contract can be moved by a single trader and should not be read as public opinion on vaccines or medicine. A price on a health contract tells readers little about public health, but it can still shape incentives around people who hold non-public information about it.