Measles is a highly contagious viral disease that can cause severe complications, including pneumonia and encephalitis. The United States declared measles eliminated in 2000, meaning no continuous transmission for over 12 months. However, outbreaks have re-emerged in recent years, driven largely by declining vaccination rates. The prediction market asks: what will the average number of measles cases be annually from 2025 to 2028, during President-elect Donald Trump's second term? This period covers January 2025 to December 2028. The market resolves to Yes if the annual average meets or exceeds a threshold set by the market creator. The question reflects growing concern about public health infrastructure, vaccine hesitancy, and the potential impact of federal policies under a new administration. Trump has previously expressed skepticism about vaccines, and his administration's first term saw the elimination of the National Security Council's global health security unit. The COVID-19 pandemic further eroded routine vaccination coverage, with CDC data showing kindergarten vaccination rates for MMR fell from 95.2% in the 2019-2020 school year to 93.1% in 2022-2023. This drop, while small in percentage, can significantly increase outbreak risk. Measles cases in the U.S. have fluctuated: 1,282 cases were reported in 2019, the highest since 1992, before falling to 13 in 2020 due to pandemic restrictions. Since then, cases have risen again, with 121 cases in 2022 and 59 in 2023. As of late 2024, the CDC reported over 280 cases for the year, suggesting an upward trend. The outcome of this market will depend on vaccination coverage, state-level exemption policies, and federal public health priorities under the new administration.

Historical Context

Measles was a common childhood illness before the vaccine was introduced in 1963. In the pre-vaccine era, the U.S. saw 3 to 4 million cases annually, with 48,000 hospitalizations and 400 to 500 deaths each year. The measles, mumps, and rubella (MMR) vaccine, licensed in 1971, drove cases down dramatically. By 2000, the CDC declared measles eliminated from the U.S. Elimination does not mean zero cases; it means no continuous transmission for more than 12 months. Imported cases from travelers continue to occur. The first major post-elimination outbreak was in 2014-2015, linked to Disneyland in California, resulting in 147 cases across seven states and Mexico. That outbreak was traced to an unvaccinated traveler and exposed gaps in herd immunity. In response, California passed SB 277 in 2015, eliminating personal belief exemptions for school vaccinations. Other states like New York and Washington later tightened exemption policies. The 2019 outbreak was the largest since elimination, with 1,282 cases concentrated in Orthodox Jewish communities in New York and Washington. The outbreak was linked to travelers from Israel and Ukraine, where vaccination rates were low. New York City declared a public health emergency and mandated vaccinations in affected neighborhoods. The COVID-19 pandemic disrupted routine healthcare globally. The CDC reported that kindergarten MMR vaccination coverage fell from 95.2% in 2019-2020 to 93.1% in 2022-2023, meaning about 250,000 kindergartners were not vaccinated against measles. The World Health Organization reported a global measles resurgence in 2023-2024, with a 79% increase in cases in 2023 compared to 2022. The U.S. has already seen outbreaks in 2024 linked to migrant shelters and unvaccinated communities.