CDC Halts Release of COVID Vaccine Study Citing Methodology Concerns

The decision to delay a C.D.C. report showing that Covid-19 vaccines reduce hospitalizations and severe illness is raising broader questions about whether scientific evidence is being sidelined as U.S. health policy shifts under political pressure

A report prepared by scientists at the Centers for Disease Control and Prevention has become the focus of an internal dispute after its publication was delayed, raising fresh questions about the handling of vaccine research under the U.S. Department of Health and Human Services.

According to reporting by The Washington Post, the study found that Covid-19 vaccines significantly reduced severe outcomes among adults. The analysis concluded that vaccinated individuals were far less likely to require urgent care or hospitalization after infection. Among healthy adults, the data showed a roughly 50 percent reduction in urgent care visits and a 55 percent drop in hospitalizations compared with those who were unvaccinated.

The report had been scheduled for publication on March 19 in the agency’s weekly journal, the Morbidity and Mortality Weekly Report, a closely watched outlet for public health findings. But its release was halted by Jay Bhattacharya, the acting director of the C.D.C., who cited concerns about the study’s methodology.

“Dr. Bhattacharya wants to make sure that the paper uses the most appropriate methodology for such a study,” Andrew Nixon, a spokesman for the Department of Health and Human Services, told the newspaper.

The delay has drawn scrutiny in part because, as The Post reported, the same methodology had recently been used in a separate analysis of influenza vaccines that was published without objection in the same journal.

The episode comes amid broader shifts in vaccine policy under the administration of Donald Trump and his health secretary, Robert F. Kennedy Jr., who has long expressed skepticism about vaccines. In 2025, the Food and Drug Administration, which operates under the health department, moved to limit access to Covid-19 vaccines.

“The secretary has already taken steps to try and remove the availability of the vaccine from children and others,” Daniel Jernigan, a former C.D.C. safety director, told The Post. “So if you’re putting out an M.M.W.R. that the vaccine is effective at preventing hospitalizations and medical care visits… that message is not line with the direction you’ve been taking with the removal of the vaccine.”

The dispute reflects a wider debate inside public health agencies over how scientific findings are communicated, particularly when they intersect with political priorities.

“He has a fixed, immutable belief that vaccines cause harm,” Paul Offit, director of the Vaccine Education Center at Children’s Hospital of Philadelphia, told The Guardian, referring to Mr. Kennedy. “He will do everything he can to try and prove that.”

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