U.S. Health officials blocked publication of a CDC study showing the Covid-19 vaccine reduced emergency department visits and hospitalizations by about half among healthy adults last winter.
The research paper had completed scientific review and received approval from Morbidity and Mortality Weekly Report editors before being halted in March, according to current and former CDC employees. It was scheduled for release on March 19 in the agency’s flagship scientific journal.
A Department of Health and Human Services spokesman confirmed the decision, citing concerns about the study’s methodological approach to estimating vaccine effectiveness. The MMWR’s editorial assessment identified issues with how researchers calculated the odds of a positive test among vaccinated versus unvaccinated patients hospitalized or visiting emergency rooms.
HHS officials did not specify exactly why the methodology was problematic in this case, though they noted prior infection, behavior, and differences in who seeks care can influence such results. The study’s authors declined to adjust their approach, according to an HHS official.
Dr. Fiona Havers, an Atlanta-based physician who previously worked at the CDC, said the wider scientific community does not share these concerns and has routinely used this method in studies published in journals including Pediatrics and the New England Journal of Medicine. She added that the approach is designed to account for care-seeking differences and that prior infection is less of an issue given widespread prior exposure to the virus.
For more on this story, see Oregon Measles Cases Rise: Health Officials Urge Vaccination.
The delay was first reported by The Washington Post after CDC’s acting director, Dr. Jay Bhattacharya, expressed reservations about the methodology. Two weeks later, the decision shifted from delay to cancellation, with officials confirming the findings would not be formally released at all.
Scientists familiar with the research said the technique used — comparing vaccination status among hospitalized or symptomatic individuals — is a standard tool for assessing real-world vaccine performance. Multiple peer-reviewed studies have employed similar designs without objection from public health agencies.
This follows our earlier report, Robert Malone Steps Down From Vaccine Panel After Judge Blocks Work.
The blocked report adds to ongoing scrutiny over how public health data is reviewed and released within federal agencies, particularly when findings conflict with political narratives about pandemic response. Critics note the timing raises questions about whether methodological concerns are being applied consistently across similar research.
Why was the study blocked if its methods have been used before?
Officials cited methodological concerns but did not explain why this particular application was problematic when the same approach has appeared in peer-reviewed journals. Independent scientists say the technique is valid and widely accepted for estimating vaccine effectiveness in observational studies.
Will the findings be made public through other channels?
There is no indication the CDC plans to publish the data elsewhere. The authors declined to revise their methodology per agency requests, and no alternative release path has been announced by HHS or CDC leadership.
