A completed CDC study showing Covid-19 vaccines cut hospitalisations and emergency department visits among healthy adults by roughly half has been blocked from publication in the agency's flagship scientific journal, according to three people with direct knowledge of the decision.

The report had cleared theCDC's full internal scientific-review process, which involves dozens of scientists, and had been scheduled for publication on 19 March 2026 in the Morbidity and Mortality Weekly Report (MMWR), the journal American public health officials have relied upon for more than 70 years. Instead, acting CDC director Jay Bhattacharya first delayed it and, as of 22 April 2026, a formal rejection letter had been issued to the report's authors.

Current and former CDC officials say it is extraordinarily rare for a paper to be pulled at that stage. The episode has deepened an already fraught debate over whetherHealth Secretary Robert F. Kennedy Jr., a longtime critic of Covid vaccines, is allowing political priorities to override scientific ones.

The suppressed study, compiled using what researchers call a test-negative design, examined people who visited emergency departments and hospitals last winter with respiratory symptoms. It compared the vaccination status of those who tested positive for Covid-19 against those who tested negative for the virus. The analysis found that vaccinated healthy adults were approximately 50 per cent less likely to be hospitalised or require emergency treatment.

Vaccine effectiveness estimates derived from this method have been published repeatedly in theNew England Journal of Medicine, the Lancet, JAMA Network Open, and Pediatrics, as well as in the MMWR itself, without methodological controversy.

The MMWR, published continuously since 1952 by theCenters for Disease Control and Prevention, is the primary channel through which the agency communicates real-time surveillance data and public health recommendations to clinicians and policymakers. Blocking a paper there does not simply delay a single finding. It removes it from the standard scientific pipeline that clinicians use to make treatment and vaccination decisions.

'This network has published in New England Journal of Medicine and The Lancet and all of these other very high-profile journals in the past,' said Dr. Fiona Havers, who resigned as a senior vaccine policy adviser at the CDC in June 2025 over Kennedy-era changes to vaccine policy. 'This seems like pretty aggressive interference by a political appointee into CDC scientific processes.'

The Washington Postfirst reportedtwo weeks earlier that Bhattacharya, who also holds the directorship of the National Institutes of Health, had delayed publication of the study. At that point, HHS spokesman Andrew Nixon told the Post it was 'routine for CDC leadership to review and flag concerns about MMWR papers, especially relating to their methodology, leading up to planned publication,' and said Bhattacharya had flagged concerns about 'the observational method used in the study to calculate vaccine effectiveness.' Following that report, Bhattacharya met with the study's authors, who declined to change their methodology.

In late March 2026, CDC scientific staff gave a presentation at Bhattacharya's request specifically explaining the test-negative design and why alternative methodologies were less efficient for measuring real-time vaccine effectiveness, asNBC News reported. There was still no resolution. On 21 April 2026, the study's authors received a formal rejection letter from the MMWR.

BLOCKED—RFK Jr’s CDC had blocked its scientists’ studying showing that the COVID booster shots reduce ER visits and hospitalizations—even among healthy adults. Already passed scientific review—CDC blocked its report from its own flagship medical journal. Disgusting.pic.twitter.com/dIlDRUlaCA

Source: International Business Times UK