Two unvaccinated Lancaster County residents have died of measles, Pennsylvania health officials said Tuesday, making them the state’s first disease fatalities in 35 years and the first reported anywhere in the U.S. this year.
The national case count is already the highest since 1991, and traders expect it to climb much further. Polymarket now gives an 87% chance the country records at least 4,000 cases this year, about 75% more than the 2,289 reported in all of 2025.
Why Traders See 4,000 Cases as the Base Case
The Centers for Disease Control and Prevention has reported 2,777 confirmed cases through Aug. 20.
From the CDC’s Aug. 20 cutoff, reaching 4,000 would require roughly 64 new cases per week through year-end. Reaching 5,000, a threshold traders price as a coin flip, would require about 117. The past three CDC updates added 94, 101 and 211 cases, averaging roughly 135 per week.
The CDC says measles can spread quickly in communities with low vaccination rates. Ninety-three percent of U.S. cases this year involve people who are unvaccinated or whose vaccination status is unknown, while 94% are linked to outbreaks.
Pennsylvania Is the Latest Hot Spot
Pennsylvania has confirmed 393 cases across 28 counties. Lancaster County accounts for 185 infections and both deaths.
Kindergarten MMR coverage in the county stood at just 87.6% during the 2025–26 school year, well below the roughly 95% level generally considered necessary to prevent sustained community transmission.
Officials declined to release the victims’ ages or medical details.
"People are not familiar with this disease and don’t fully understand the potential severity of the illness," Pennsylvania Health Secretary Dr. Debra Bogen said, noting that measles had been largely eliminated in the state for more than three decades.
Where Merck and GSK Fit In
Merck & Co. Inc. (NYSE:MRK) makes M-M-R II and ProQuad, while GSK plc (NYSE:GSK) makes Priorix. Together, Merck and GSK manufacture all three FDA-licensed measles-containing combination vaccines available in the U.S.
For investors, the outbreak is a modest demand tailwind rather than an earnings catalyst. Merck has more to gain and has previously said outbreaks boosted M-M-R II sales.
The companies are also at odds with the White House. President Donald Trump said this month that the combined MMR vaccine could be "quite lethal," while separate shots appeared "not at all lethal." Merck and GSK rejected his push, saying there is no evidence separate shots are safer or more effective.
CMS Administrator Dr. Mehmet Oz later contradicted the president, telling CBS: "The MMR vaccine is not a lethal vaccine."
The broader test arrives in November, when the Pan American Health Organization reviews whether the U.S. has lost the measles elimination status it has held since 2000.
Image: Shutterstock
Login to comment