On April 22, 2026, the Department of Health and Human Services (HHS) halted publication of a study that found the Covid-19 vaccine cut emergency room visits and hospitalizations among healthy adults by roughly half. The research paper was scheduled for publication in the March 19 edition of the Morbidity and Mortality Weekly Report (MMWR), the Centers for Disease Control and Prevention (CDC)’s principal publication.
HHS spokesperson Andrew Nixon cited “concerns regarding the methodological approach to estimating vaccine effectiveness” following an MMWR editorial assessment as the reason for blocking the report. According to current and former CDC employees, however, the paper had already undergone scientific review and been approved by the MMWR editors.