Online prediction markets Polymarket and Kalshi have started allowing users to place bets on US public health outcomes, including measles cases, vaccine approvals and drug trial results. The platforms position themselves as financial derivatives rather than traditional gambling, operating under federal commodities laws overseen by the US Commodity Futures Trading Commission rather than being regulated by states as gambling operations. Users can wager on when the FDA will approve a skin-cancer vaccine, whether the CDC will change its vaccine recommendations, how many measles cases the US might see in 2026, and whether the country will lose its measles-elimination status this year. Polymarket has advertised these offerings through public signs, including one posted on a construction fence next to an elementary school in Brooklyn.
The emergence of health-related betting contracts has drawn warnings from public health experts about potential conflicts of interest. Matthew Eisenberg, professor and chair of health policy and management at Johns Hopkins Bloomberg School of Public Health, noted that prediction markets could create incentives for insider trading. Those with access to non-public information, such as FDA reviewers, trial investigators and legislative staff, could profit from leaks about regulatory decisions or trial outcomes. Eisenberg warned that advocates and officials could potentially place bets on outcomes like ending vaccine mandates and then introduce policies to influence those outcomes, though no laws appear to prohibit this practice. He cautioned that predictions on smaller contracts can be moved by single traders and should not be interpreted as public sentiment.
Lia Nower, director of the Center for Gambling Studies at Rutgers University, described prediction markets as functionally identical to regulated gambling but operating in a regulatory loophole. She said the federal government has no regulatory body prescribing limits or minimum guidelines for states to follow. Prediction markets could affect how drugs are tested and regulated, with trial participants potentially changing their behaviour to influence outcomes or drug companies altering trial timings. Nower highlighted that gambling is a growing public health concern disproportionately affecting younger, Black or Hispanic and lower-income people. A recent report she co-authored found that more than half of young people between ages 13 and 27 gambled in the past year, with 39.5% of young gamblers showing some degree of gambling-related risk and 10.3% at high risk for problem gambling.
Kalshi argued that its clinical trial markets, presented as a pilot programme, would improve transparency in drug development by making insights from people with specialised knowledge available to the public. However, Polymarket did not respond to questions about the potential consequences for public health or medicine. Several states have filed lawsuits against the companies alleging they function as gambling sites. New Jersey is among states moving to restrict the markets, citing concerns about consumer protection and insider trading. Eisenberg characterised the situation as pointing toward a future of "gambling on everything, everywhere, with fewer and fewer consumer protections."
For savers, borrowers, business owners and investors in the UK, these developments in US prediction markets highlight how financial innovation can outpace regulatory frameworks, creating risks that may eventually spread to other jurisdictions.