CDC Acting Director Blocks MMWR Publication of 2025-2026 COVID Vaccine Effectiveness Study Later Released in External Journal

The study, initially cleared through CDC scientific review for MMWR, was halted by Acting Director Jay Bhattacharya over methodological concerns despite editorial approval. It employed a test-negative design comparing vaccinated and unvaccinated adults presenting with COVID-like illness, documenting roughly 50% lower rates of emergency, urgent, and inpatient care among recipients even after prior vaccination and infection. Publication occurred months later in an independent journal following Washington Post reporting on the delay.

The episode highlights tensions between internal CDC gatekeeping and external dissemination of observational data on real-world vaccine performance. While the findings align with prior estimates of moderate effectiveness against severe outcomes in previously immune populations, the blocking raises questions about transparency thresholds applied to vaccine surveillance studies versus other public health analyses. Experts note the design reflects current epidemiology but cannot isolate causal effects without randomization.

Future policy impact hinges on whether similar VE estimates hold in larger datasets tracking absolute hospitalization rates. Regulators may face pressure to release raw surveillance data for independent reanalysis if patterns of selective publication recur.

Next steps include replication in additional seasons and integration with immunogenicity data to clarify duration of protection.