The Department of Health and Human Services has issued another stop work order for Vaxart's oral COVID-19 vaccine trial, marking the second regulatory freeze for the California biotech's $460.7 million federally-funded program. The August 5, 2025 order halted patient screening and enrollment for the Phase IIb study of VXA-CoV2-3.3, though participants already dosed can continue per-protocol follow-up.
Trial Progress and Regulatory Action
Vaxart had enrolled approximately 5,000 participants—roughly half of its 10,000-patient target—when the stop work order was delivered through Advanced Technology International, a nonprofit manager of R&D collaborations. The mid-stage comparative study, which began dosing in May 2025, was designed to evaluate the oral vaccine against Pfizer and BioNTech's mRNA-based Comirnaty across the large patient population.
According to Vaxart's SEC filing, the company "has, to date, not been provided with any further details, including the reason for such stop work order." The regulatory action came despite the independent Data Safety Monitoring Board's July 14, 2025 determination that "the study could continue to proceed without modification."
Broader Policy Context
The timing of the stop work order aligned precisely with HHS's announcement to wind down mRNA vaccine development activities under the Biomedical Advanced Research and Development Authority (BARDA). The federal agency canceled or de-scoped more than 20 projects worth nearly $500 million combined on the same day Vaxart received its order.
While Vaxart was not specifically named among companies facing contract terminations in the HHS press release, an HHS spokesperson directed inquiries about the Vaxart order to the broader August 5 announcement about mRNA program changes. Notably, Vaxart's VXA-CoV2-3.3 is a protein-based oral vaccine, though the company uses an mRNA vaccine as a control arm in its Phase IIb trial.
Vaccine Technology and Development
VXA-CoV2-3.3 represents an orally available S-protein COVID-19 vaccine designed to elicit durable immunity against SARS-CoV-2 variants. Preclinical data demonstrated the investigational pill's potential to reduce airborne transmission by minimizing viral shedding, offering a differentiated approach from existing injectable vaccines.
The oral vaccine program has faced significant regulatory turbulence over recent months. A previous stop work order in February 2025 prompted Vaxart to lay off 10% of its workforce before the freeze was lifted in late April. The current trial was originally scheduled to complete in November 2026.
Financial and Operational Impact
BARDA's funding commitment to Vaxart reached $460.7 million as of February 2025, representing a substantial federal investment in oral vaccine technology. The repeated regulatory interruptions have created operational challenges for the South San Francisco-based clinical-stage biotechnology company, which specializes in oral solid-dose recombinant vaccines.
The stop work order allows Vaxart to continue follow-up activities for participants who have already received doses, but prevents further patient recruitment and screening activities. This partial continuation maintains some study continuity while regulatory authorities conduct their review process.
