Key facts
- Kalshi began offering health-related predictions over the summer of 2026, and Polymarket has since joined it.
- Users can bet on FDA approval of a skin-cancer vaccine and on CDC changes to vaccine recommendations.
- Bets also cover measles case counts in the US in 2026 and whether it loses measles-elimination status that year.
- Kalshi spokesperson Dani Lever said the clinical trial markets are a pilot program aimed at a structural problem in drug development.
- Polymarket did not respond to the Guardian's questions on the consequences for public health or medicine.
- A Polymarket sign in Brooklyn was vandalized within a week, with the portion on placing a prediction ripped away.
Polymarket and Kalshi, two online prediction markets, are hosting contracts on US public health outcomes, the Guardian reported on November 14, 2026. Kalshi began offering health-related predictions over the summer of 2026, and Polymarket has since joined it, advertising a vaccine-market contract on a sign pasted on a construction fence next to an elementary school in the Brooklyn borough of New York City.
Users can wager on when the US Food and Drug Administration will approve a skin-cancer vaccine, whether the US Centers for Disease Control and Prevention will change its vaccine recommendations, drug trial outcomes and approvals, how many measles cases the US might see in 2026 and whether it will lose its measles-elimination status that year.
Matthew Eisenberg, professor and chair of health policy and management at the Johns Hopkins Bloomberg School of Public Health, said he was not surprised: "Kalshi and Polymarket will list contracts on anything with a checkable outcome." Lia Nower, a professor and the director of the Center for Gambling Studies at Rutgers University, said prediction markets are functionally identical to regulated gambling but largely unregulated, and that they position themselves as financial derivatives under federal commodities laws with oversight from the US Commodity Futures Trading Commission. Several states have filed lawsuits alleging the companies function as gambling sites.
Nower said advocates, officials and lawmakers could bet on ending vaccine mandates at the state level and then introduce policies to do so, and that there do not appear to be laws against that. Eisenberg said predictions on FDA decisions and trial endpoints create a payoff for anyone with nonpublic information, such as agency reviewers, trial investigators and legislative staff, and that the risk is that the market rewards leaks.