The Centers for Disease Control and Prevention has blocked publication of a study showing Covid-19 vaccines cut emergency department visits and hospitalizations by roughly half among healthy adults last winter, according to multiple sources familiar with the decision.
The report, which had cleared the agency’s scientific review and was scheduled for the March 19 edition of the Morbidity and Mortality Weekly Report, was ultimately rejected after concerns were raised about its observational methodology for estimating vaccine effectiveness.
Sources told The Washington Post that the study found vaccinated healthy adults reduced their risk of urgent care and emergency room visits by 50 percent and Covid-related hospitalizations by 55 percent compared to unvaccinated peers between September and December 2025.
A former CDC official said halting an MMWR report at this late stage — after scientific clearance and editorial review — is highly unusual, noting that timing shifts typically occur only to align with broader communications plans.
The Department of Health and Human Services said the decision was based on methodological concerns, with a spokesman stating the MMWR’s editorial assessment identified issues with the approach to estimating vaccine effectiveness and the manuscript was not accepted for publication.
For more on this story, see CDC blocks study showing COVID-19 vaccines cut hospitalizations by 50%.
Jay Bhattacharya, who is overseeing the CDC pending Senate confirmation of Dr. Erica Schwartz as director, initially delayed the report over methodology questions, according to The Independent, which noted his concerns were being addressed before the study was shelved entirely.
Some current and former officials worry the suppression of positive vaccine data could align with administration efforts to limit vaccine use, though HHS Secretary Robert F. Kennedy Jr. Has said his goal is to increase transparency and give people more choice.
The study’s findings on reduced hospital strain during peak respiratory season could have informed vaccination timing recommendations for the upcoming fall, particularly for healthier adults weighing individual risk.
By withholding data showing measurable public health benefits, the decision risks creating an information gap as states and providers prepare for seasonal vaccine campaigns amid evolving public skepticism.
Why was the study blocked if it had already passed scientific review?
Officials cited concerns about the observational method used to calculate vaccine effectiveness, stating the MMWR’s editorial assessment found the methodological approach unsuitable for publication despite prior scientific clearance.
What does this mean for future CDC reports on vaccine effectiveness?
The incident raises questions about whether methodological scrutiny could be applied inconsistently, potentially chilling the release of favorable data even when studies meet internal scientific standards.
