The CDC Had Evidence That Last Winter’s COVID Vaccine Worked. It Didn’t Publish It.
A study showing last winter’s COVID vaccine cut emergency room visits and hospitalizations in healthy adults by roughly half was blocked from publication in the MMWR, the CDC’s own journal. The agency’s acting director raised methodology concerns. Scientists outside HHS say the methods are standard and widely used.
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They’re more likely to experience long COVID than men, and COVID during pregnancy raises the risk of preterm birth, stillbirth, and ICU admission. The suppressed data wasn’t marginal. It was directly relevant to the population most affected by COVID’s long-term consequences.
The MMWR, the Morbidity and Mortality Weekly Report, is the CDC’s primary vehicle for publishing public health surveillance data. It is not a peer-reviewed journal in the traditional sense, but it carries significant clinical weight. Physicians, public health officials, and hospital systems use it to inform practice. When a study is completed and ready, blocking it from publication is not a routine editorial decision.
Sources familiar with the situation told reporters the methodology used was an established design that the CDC has published using routinely. The acting director’s objection was not that the study was flawed in a novel way, but that the agency chose not to release it at a particular moment.
Long COVID affects an estimated 10-30% of people who have had COVID-19, with women consistently overrepresented in that population. The reasons are not fully understood but likely involve immune system differences and hormonal factors. For pregnant women, the stakes are higher still: COVID infection during pregnancy is associated with significantly elevated rates of preterm delivery, stillbirth, and maternal ICU admission, making vaccine effectiveness data directly relevant to obstetric decision-making.
The study’s suppression means clinicians counseling patients on whether to get vaccinated this year are doing so without data the federal government collected, analyzed, and then chose not to share. That gap is not neutral.
Source: Reporting on CDC MMWR publication decision, May 2026. Study examined COVID vaccine effectiveness in reducing ER visits and hospitalizations in healthy adults during winter 2025-2026.