The Centers for Disease Control and Prevention (CDC) has canceled publication of a scientific report showing the efficacy of the COVID-19 vaccine, according to media reports.

The Washington Post, which first reported the news, says the report, initially scheduled to be published in the CDC’s Morbidity and Mortality Weekly Report on March 19, showed the COVID-19 vaccine cut the likelihood of emergency department visits and hospitalizations in half this past winter. 

The report had cleared the agency’s scientific review process before being delayed by acting CDC Director Jay Bhattacharya, MD, PhD, over concerns about the methodology. But the same methodology has long been used by the CDC to evaluate vaccine effectiveness for respiratory viruses and was used in a study on the flu vaccine published last month in MMWR.

In response to a query from CIDRAP News, a CDC official did not address the blocked report specifically but said the agency has to apply the “highest standards of scientific rigor” to the information it publishes.

“Responsible science requires careful review. Taking time to ensure analyses are methodologically sound and clearly communicated is always preferable to risking error,” the official said.

An unprecedented move

A former CDC official said he wasn’t aware of a report that was already cleared and scheduled for publication in MMWR being blocked by leadership during his time at the agency.

“Suppressing the standard of science on VE [vaccine efficacy] to wait for a perfect study in a system that cannot support it is not a hallmark of transparent scientific expertise,” Demetre Daskalakis, MD, MPH, the former director of the CDC’s National Center for Immunization and Respiratory Diseases, said in an email.

The news comes at a time when the Trump administration has been seeking to downplay efforts by Health and Human Services (HHS) Secretary Robert F. Kennedy Jr., who oversees the CDC, to undo US vaccine policies ahead of the midterm elections. In May 2025, Kennedy announced that the COVID-19 vaccine, which he once called “the deadliest vaccine ever made,” would no longer be recommended for pregnant women and healthy children. 

Suppressing the standard of science on VE [vaccine efficacy] to wait for a perfect study in a system that cannot support it is not a hallmark of transparent scientific expertise.

Daskalakis said the cancelation of the report appears to be “cherry picking based on the bias of the director and others at HHS who don’t fully understand the importance of the methods used to assess the added benefit of vaccines in preventing poor outcomes.”

The CDC has been without a confirmed director since Susan Monarez, PhD, was pushed out on August 27, 2025, after clashing with Kennedy over vaccine policy and his request that she fire top CDC officials. Daskalakis and three other top CDC officials resigned in response. In congressional hearings this week, Kennedy refused to commit to supporting the vaccine recommendations of Erica Schwartz, MD, JD, MPH, the Trump administration’s recent nominee to lead the agency.