Study on Covid Vaccine Effectiveness Published After Being Blocked

A recent study on Covid vaccines, which was initially blocked from publication by the acting director of the Centers for Disease Control and Prevention, has now been released in a different journal. This study was made public on Tuesday.

The findings indicated that Covid vaccines cut the chances of severe illness by approximately 50% among adults during the last fall and winter seasons. Originally, this study was slated for release in March in the CDC’s main scientific journal, the Morbidity and Mortality Weekly Report (MMWR). However, instead, it found a home in JAMA Network Open, a respected peer-reviewed journal from the American Medical Association.

Concerns were raised by Acting Director Jay Bhattacharya regarding the study’s methodology, even after it received approval through scientific review. Current and former CDC staff shared with NBC News in April that Bhattacharya questioned the approach of the study, which employed a “test-negative design.” This design compares the vaccination statuses of individuals testing positive for Covid and those testing negative.

The study examined adults who visited hospitals or urgent care facilities for symptoms consistent with Covid, spanning across seven states from September to December of the previous year. Patients were tested around the time of their medical visits. The researchers then computed the odds of having received the 2025-26 version of the Covid vaccine. They discovered that vaccination reduced the necessity for emergency or urgent care by 50% and decreased hospitalization by 55%.

Some experts in public health perceived Bhattacharya’s decision to halt the study as political meddling, suggesting it was a means to suppress evidence regarding vaccine safety. Notably, Health and Human Services Secretary Robert F. Kennedy Jr., known for his longstanding anti-vaccine views, had previously labeled the Covid vaccine as “the deadliest vaccine ever made.”

Bhattacharya expressed that he preferred longitudinal cohort studies, which follow larger groups over extended periods, considering them to be more robust. This method would involve tracking vaccinated against unvaccinated individuals over time and measuring illness incidences. Yet, it’s worth noting that such studies generally require more time and funding compared to test-negative designs.

In response to inquiries about the withdrawal, a Health and Human Services Department spokesperson emphasized that the CDC is committed to public health by delivering accurate and trustworthy information, thus necessitating high scientific standards, particularly when findings impact clinical decisions like vaccinations.

The newly published study maintains that the test-negative design offers a “convenient and efficient method” for evaluating vaccine efficacy in real-world contexts. Researchers outside the study have acknowledged its advantages, stating it is cost-effective and yields timely findings, allowing comparison between groups with similar propensities for seeking medical assistance.

However, the study isn’t devoid of limitations. Individuals visiting hospitals or urgent care might have greater trust in the healthcare system, leading them to be more inclined to get vaccinated than the general populace. Additionally, those who tested negative often had other respiratory issues, suggesting they weren’t entirely well.

In a prior op-ed featured in The Washington Post, which first spotlighted the MMWR study’s retraction, Bhattacharya noted that the test-negative design overlooks data from individuals who were never hospitalized. He also emphasized that factors like prior Covid infections could potentially skew the findings.

He wrote that the estimates of vaccine effectiveness derived from this method could either overstate or understate reality, though it remains challenging to determine which.

The CDC has recently organized a public debate discussing the merits and shortcomings of varying vaccine effectiveness studies, including the aforementioned cohort studies and randomized controlled trials that compare vaccinated groups against those receiving a placebo.

Natalie Dean, an associate professor of biostatistics at Emory University, commented that researchers have long recognized the constraints of test-negative studies but generally concur that these limitations do not compromise their conclusions. It certainly feels strange that this has seemingly become the crux of what determines a study’s publication in MMWR, she mused.

Dean, who reviewed the peer process for the JAMA Network Open study but did not partake in the research, asserted that the work’s quality remained unchanged since the CDC’s review. In a Tuesday editorial coinciding with the study’s release, she described the test-negative design as an “important and practical approach” for assessing vaccine efficiency. Instead of abandoning this methodology, she suggested enhancing health records to provide more comprehensive details about tested populations.

“I worry that it could become entangled in some cultural conflict, and it’s such a vital tool,” she expressed in a recent interview.