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# JAMA Publishes Previously Blocked Covid-19 Vaccine Study
- URL: https://www.fdaweb.com/jama-publishes-previously-blocked-covid-19-vaccine-study/
- Published: 2026-06-24T12:00:00.000Z
- Updated: 2026-09-14T13:41:52.000Z
- Author: David McFarland
- Tags: Biologics, #legacy-id-D5161363

A Covid-19 vaccine effectiveness study that was previously blocked from publication in a Centers for Disease Control and Prevention (CDC) journal has now been published in [*JAMA Network Open*](https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2850668?utm%5Fsource=newsletter&utm%5Fmedium=email&utm%5Fcampaign=newsletter%5Faxiosvitals&stream=top), reigniting a debate over both vaccine policy and the methods used to evaluate vaccine performance. The study found that the 2025-2026 Covid-19 vaccine was about 55% effective in preventing Covid-19-associated hospitalizations and 50% effective in preventing emergency department and urgent care visits among immunocompetent adults. Researchers used data from the CDC's VISION Network, which tracks vaccine effectiveness across multiple healthcare systems.

The paper attracted attention earlier this year after HHS officials banned its planned publication in the CDC's *Morbidity and Mortality Weekly Report* (MMWR), citing concerns about the study's methodology. The decision fueled accusations of political interference under HHS secretary **Robert F. Kennedy Jr.** and the Trump administration.

At the center of the dispute is the study's use of the "test-negative design," a case-control methodology widely employed in many vaccine effectiveness studies. Under this approach, researchers compare vaccination rates among patients who seek care for similar respiratory symptoms but test positive versus negative for the target pathogen.

The study's publication was accompanied by a [commentary](https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2850669?ref=fdaweb.com) defending the methodology, with vaccine experts arguing that the test-negative design remains one of the most practical and scientifically valid approaches for generating real-time vaccine effectiveness estimates. The authors noted that the method has been used for decades and has become a standard tool for monitoring vaccine performance during rapidly evolving outbreaks.

Critics, however, continue to challenge the approach. Among the most prominent are NIH Director **Jay Bhattacharya** and biostatistician **Martin Kulldorff**, who have argued that test-negative studies can produce biased estimates because of differences in prior infection, healthcare-seeking behavior, and other confounding factors between vaccinated and unvaccinated populations. Those concerns were cited by HHS officials when the CDC publication was halted earlier this year.