A COVID-19 vaccine effectiveness study that was blocked from the CDC’s flagship journal was published June 23 in JAMA Network Open.
Five things to know:
1. The study found the 2025-26 COVID-19 vaccine reduced the likelihood of emergency department and urgent care visits by 50% and hospitalizations by 55% among immunocompetent adults. Researchers analyzed more than 85,700 ED and urgent care encounters and 26,000 hospitalizations across 179 hospitals in seven states between September and December 2025.
2. The paper had cleared the CDC’s full internal scientific review and was approved for publication in the Morbidity and Mortality Weekly Report before National Institutes of Health Director Jay Bhattacharya, MD, PhD, intervened in March.
3. Dr. Bhattacharya, who is leading the CDC until a permanent director is named, raised concerns about the study’s test-negative methodology — a design the CDC has used routinely to assess vaccine effectiveness for respiratory viruses. Dr. Bhattacharya told NBC News he favors longitudinal cohort studies that track vaccinated and unvaccinated people over time, though this research is more time-consuming and costly.
“The CDC protects the public’s health by providing accurate, transparent, and trustworthy information,” an HHS spokesperson told the publication. “This requires applying the highest standards of scientific rigor, especially when findings may influence clinical decisions such as immunization.”
4. In an accompanying editorial published in JAMA Network Open, Natalie Dean, PhD, an associate professor at Emory University’s Rollins School of Public Health, called the test-negative design “an important and practical approach” for vaccine monitoring and said the study’s quality had not changed since the CDC’s own scientific review approved it. Rather than abandoning the methodology, Dr. Dean said test-negative studies could be strengthened by improving health records to capture more detail about who is being tested. Dr. Dean participated in the peer review process for the study, but was not part of the research.
5. The study’s publication comes as HHS Secretary Robert F. Kennedy Jr. faces ongoing scrutiny over his administration’s approach to vaccine policy and federal health agency oversight.
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