CDC Acting Director Delays Release of Study Showing Covid Vaccine Benefits

Concerns over study's methodology prompt hold on publication in agency's scientific journal

Apr. 10, 2026 at 8:38pm

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A ghostly, translucent X-ray photograph of a syringe filled with a glowing liquid vaccine, against a dark background, revealing the intricate internal structure of the syringe in a conceptual illustration of the scientific rigor and transparency required in vaccine research.An X-ray image reveals the inner workings of a vaccine syringe, highlighting the scientific scrutiny needed to ensure public trust in immunization research.Washington Today

The Centers for Disease Control and Prevention was expected to publish a study last month showing that Covid vaccines reduced the likelihood of severe illness, but the agency's acting director, Dr. Jay Bhattacharya, delayed its release due to concerns about the methodology. Some current and former CDC employees worry the move represents political interference in the agency's scientific process.

Why it matters

The delayed study is seen as part of a broader effort by the Trump administration to sow doubt in vaccine safety and make vaccines less available to the public. This comes as the administration has pledged to restore 'gold-standard science' to federal health agencies, raising concerns that the goal is to invalidate studies that don't align with the administration's views on vaccines.

The details

The study, which was scheduled to be published in the CDC's Morbidity and Mortality Weekly Report (MMWR), used a common methodology known as a test-negative design to evaluate the effectiveness of Covid vaccines. This approach compares the vaccination status of people who tested positive for Covid to those who tested negative. Several other recent MMWR papers have used the same methodology. However, Bhattacharya, a political appointee tapped to run the CDC, expressed concerns about the observational method and delayed the study's release.

  • The study was scheduled to be published on March 19.
  • Bhattacharya requested a presentation in late March from CDC employees explaining the test-negative design methodology.

The players

Dr. Jay Bhattacharya

The acting director of the Centers for Disease Control and Prevention who delayed the release of a study showing the benefits of Covid vaccines due to concerns over the methodology.

Robert F. Kennedy Jr.

The Health Secretary who oversees federal health agencies including the CDC and has a long history of anti-vaccine activism.

Fiona Havers

A former medical epidemiologist at the CDC who oversaw the agency's Covid hospitalization data and resigned in protest after Kennedy fired the CDC's vaccine advisory committee.

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What they’re saying

“It's routine for CDC leadership to review and flag concerns about MMWR papers, especially relating to their methodology, leading up to planned publication. Dr. Bhattacharya wants to make sure that the paper uses the most appropriate methodology for such a study.”

— Andrew Nixon, Spokesperson for the Department of Health and Human Services

“I'm not saying that they haven't stopped other publications or forced changes to them, but to wholesale stop this report from coming out, given that it is such a well-established platform and such a well-established methodology, does strike me as a new level of political interference into CDC's scientific process.”

— Fiona Havers, Former medical epidemiologist at the CDC

What’s next

It's unclear if or when the delayed study will be published by the CDC. If it does not wind up in the MMWR, the authors may submit it to an independent medical journal for publication.

The takeaway

This incident highlights concerns about political interference in the scientific process at federal health agencies under the Trump administration, which has pledged to restore 'gold-standard science' while also sowing doubt about vaccine safety and availability.