U.S. health officials have stopped the publication of a study on whether the COVID-19 vaccine was keeping adults from becoming sick enough to have to go to the hospital.
A U.S. Department of Health and Human Services spokesman on Wednesday confirmed the decision to halt publication, citing a dispute about the study’s methodology.
The research paper was to appear in Morbidity and Mortality Weekly Report, the Centers for Disease Control and Prevention’s flagship publication.
One way scientists have studied COVID-19 vaccine effectiveness is by focusing on sick people who were admitted to hospitals or visited emergency rooms. The researchers check whether patients were vaccinated and then calculate the odds of a positive COVID-19 test among vaccinated patients vs. those who were unvaccinated.
Papers using that methodology have been published — after review by experts in the field — in a number of esteemed journals, including Pediatrics and the New England Journal of Medicine.
Following the same approach, the new study concluded that the vaccine cut ER visits and hospitalizations among otherwise healthy adults by about half this past winter, according to The Washington Post, which first reported the cancellation.
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HHS officials did not say exactly why that methodology was a problem in this instance but argued that prior infection, behavior and differences in who seeks care can affect results.
The wider scientific community does not have those concerns and many researchers have used the approach, said Dr. Fiona Havers, an Atlanta-based doctor who previously worked at CDC. The methodology is built to address differences related to who seeks care, and prior infection shouldn’t be much of an issue because so many Americans have been infected by the coronavirus, she added.
No study design is perfect, but HHS officials haven’t proposed an alternative “that’s realistic and ethical for getting real-time estimates of how well vaccines are working each year,” said Havers, who once led a CDC hospital network surveillance team that focused on COVID-19 and other respiratory viruses.
During President Donald Trump’s first administration, public health advocates worried that political appointees were trying to control what was being published in the MMWR.
Those concerns returned last year, when Trump returned to office and publication of the MMWR was temporarily suspended. It returned, but has remained a thinner version of its former self.
“Health care professionals rely on the MMWR for timely, objective and fact-based information about the nation’s public health,” said U.S. Sen. Dick Durbin, an Illinois Democrat who voiced concern when CDC communications were halted last year.
“Muzzling scientists and doctors on how to prevent Americans from being hospitalized can have deadly consequences. The CDC must abandon plans to place a political gag order on this critical research,” Durbin said in a statement Wednesday.
© 2026 The Canadian Press