Blocked CDC vaccine study finds 55 percent protection against hospitalization

A COVID-19 vaccine study that was pulled from the Centers for Disease Control and Prevention’s flagship journal found the 2025-26 shot was about 55 percent effective at preventing COVID-19-associated hospitalization and cut emergency-department and urgent-care visits by about 50 percent. The paper was published June 23, 2026, in JAMA Network Open after being blocked from the Morbidity and Mortality Weekly Report.

The study looked at adults age 18 and older without weakened immune systems who sought care for COVID-like illness at CDC Vaccine Effectiveness Network sites in California, Colorado, Georgia, Indiana, Maryland, Minnesota, New York, Oregon, Texas and Utah. Researchers used data from September through December 2025, focusing on the 2025-26 COVID-19 vaccine formulation.

At the center of the dispute is the test-negative design, a standard observational method in vaccine research that compares vaccination status among people who sought care for respiratory symptoms and then tested positive for SARS-CoV-2 with those who tested negative. Natalie Dean of Emory University Rollins School of Public Health wrote in an accompanying JAMA Network Open editorial that the test-negative design remains an important and practical approach, especially while other methods continue to mature. The paper also appeared alongside a secondary cross-protocol analysis of five phase 3 COVID-19 Prevention Network randomized clinical trials meant to assess the accuracy and precision of that design.

The CDC had originally scheduled the study for publication in MMWR in the spring, and it had already gone through internal scientific review and received editorial approval before publication was halted. Acting CDC Director Jay Bhattacharya raised concerns about the methodology, including objections to the test-negative design, while U.S. Department of Health and Human Services spokesman Andrew Nixon said scientific reports are reviewed at multiple levels and that the MMWR editorial assessment identified concerns about the method used to estimate vaccine effectiveness.

MMWR has long been used for rapid dissemination of public-health findings, including routine vaccine-effectiveness estimates from CDC-supported networks such as VISION.