Moderna Scraps Norovirus Vaccine Cohort Enrollment
The company will meet with regulators to decide next steps for its mRNA-1403 phase 3 trial after cutting plans for a new cohort.
Updated on Nov. 6, 2026 in Biotech
Moderna has scrapped plans to enroll a new cohort in its phase 3 norovirus vaccine trial, following a review of the program. The company is engaging with health authorities to determine next steps for mRNA-1403.
Why it matters
The decision follows a series of setbacks for the candidate, including a missed interim analysis, an FDA clinical hold over a reported Guillain-Barré syndrome case, and an extended study timeline. The outcome will shape whether the mRNA-based norovirus vaccine advances.
Moderna's third-quarter R&D expenses dropped 27% to $583 million, reflecting lower clinical development costs and cost efficiencies. Whether the mRNA-1403 program will receive further funding or continue in any form remains unresolved.
The players
Moderna
Moderna is a biotechnology company known for its mRNA vaccine platform, which underpinned its COVID-19 vaccine.
U.S. Food and Drug Administration
The FDA is the U.S. federal agency responsible for regulating drugs and vaccines, and it placed the mRNA-1403 trial on hold in February 2025.
The details
mRNA-1403 is a trivalent vaccine designed to prevent acute gastroenteritis. The phase 3 trial launched in September 2024, and Moderna disclosed in July that the candidate missed its interim analysis.
Timeline
September 2024: Phase 3 mRNA-1403 trial launched.
February 2025: FDA placed mRNA-1403 on hold over a reported Guillain-Barré syndrome case.
November 2025: Study extended for a second Northern Hemisphere season after failing to find enough cases in the Southern Hemisphere.
November 6, 2026: Moderna announced on its earnings call that cohort enrollment was scrapped.
Roadmap
Moderna's norovirus program is a test of whether its mRNA platform, proven with its COVID-19 vaccine, can be extended to other pathogens. The setbacks on mRNA-1403 show that platform success does not automatically carry over to new targets.
A halted or delayed norovirus vaccine would leave the millions of people who suffer seasonal gastroenteritis without a preventive option for longer. Readers should watch for Moderna's update on whether the trial proceeds, since that will determine when any approved product could reach the public.
The takeaway
Vaccine development timelines often slip when trials face safety signals or insufficient case counts, so new candidates should be followed through regulatory checkpoints rather than launch announcements. Moderna's next update will show whether mRNA-1403 can still reach approval.
What happens next
Moderna will provide further updates following discussions with health authorities on the next steps for mRNA-1403.
Further reading
For more on the research pipelines behind these candidates, see Biotech.
Source note: This article includes information reported by FierceBiotech - free daily biotech briefing.
