Full Breakdown
CDC Blocked COVID-19 Vaccine Effectiveness Study, Prompting Debate Over Test-Negative Design
6/24/2026, 8:15:47 AM
Study Publication After CDC Block
Researchers completed a test-negative design study estimating COVID-19 vaccines to be ~55 % effective against hospitalizations and to reduce emergency-department and urgent-care visits by ~50 %. Although cleared by the CDC’s Office of Science, acting CDC director Jay Bhattacharya flagged the manuscript for further review. The authors then published the paper in *JAMA Network Open* on Tuesday.
Methodology and Stakeholder Perspectives
The test-negative design compares vaccination status of patients with respiratory illness who test positive versus negative for COVID-19, a method employed in journals such as *Pediatrics* and *NEJM*. CDC acting director Jay Bhattacharya raised concerns about its assumptions; Emory biostatistician Natalie Dean defended it; HHS biostatistician Martin Kulldorff, co-author of the Great Barrington Declaration, criticized its inclusion criteria.
Study Findings
The analysis showed a 55 % reduction in COVID-19-related hospitalizations and a 50 % decline in urgent-care visits among vaccinated patients, reflecting effectiveness amid evolving viral strains and shifting immunity.
Official Statements & Responses
CDC officials said the U.S. Department of Health and Human Services has not proposed an alternative method for timely vaccine-effectiveness data. CDC chief science officer Althea Grant-Lenzy noted authors could publish elsewhere after addressing CDC concerns. HHS has offered no substitute, keeping the test-negative design as the main real-time tool.
Criticism & Opposition
Jay Bhattacharya warned that the design’s reliance on assumptions about prior infection and patient behavior could skew results. Martin Kulldorff, co-author of the Great Barrington Declaration, questioned the inclusion of patients with other diseases and urged longer-term cohort studies.
Why It Matters
Accurate, up-to-date vaccine-effectiveness estimates guide public-health policy, resource allocation, and booster decisions, highlighting the tension between rapid data and methodological rigor.
Verbatim Quotes
- “The vaccine was found to be about 55% effective against COVID-19-associated hospitalizations, and reduced COVID-19-related trips to emergency departments and urgent care clinics by 50%, according to the study published Tuesday by JAMA Network Open.” — Study authors, *JAMA Network Open*
- “It is critical that we continue to characterize and publish estimates of vaccine effectiveness in populations with changing immunity against evolving viral strains,” — Natalie Dean, Emory University biostatistics expert
- “The study approach, called “test-negative design,” looks at people who were admitted to hospitals or visited emergency rooms with respiratory illnesses.” — Study authors, *JAMA Network Open*
- “We were in a pandemic! That's why!” — Audience member, CDC forum
What’s Next
The CDC’s recent forum on test-negative studies gathered supporters and critics. Continued debate will shape future guidance on real-time vaccine-effectiveness monitoring.
