Competing with giants like Takeda and Moderna, the plucky biotech believes it has unlocked a future with an easy, yearly oral vaccine.
Norovirus is a nasty, fast-acting virus that has confounded all efforts to quell it. Vaccine manufacturer Vaxart thinks it has found the answer in a cheap, easy-to-take and repeatedly doseable vaccine—potentially ahead of bigger peers Takeda and Moderna.
Anyone who has kids, or who’s been on a cruise, knows that norovirus can get you over and over again, as if your immune system doesn’t learn anything from the experience. “Even if it’s the same strain,” Vaxart founder and CSO Sean Tucker told BioSpace in an interview on the sidelines of the J.P. Morgan Healthcare Conference in January.
So what’s the best way to get someone that immunity? A vaccine. And the best way to get someone to take a vaccine? It’s not an injection; it’s a pill, Tucker said.
Vaxart wanted to “build something that’s simple, cheap and easy to use, and give that as a vaccine,” he continued. “Because it’s hard to develop long-term immunity, just handing out tablets every year would be very simple.”
Well-Positioned, Well-Timed
There is no approved norovirus vaccine available anywhere in the world, or any targeted treatment for the virus, which is the leading cause of vomiting and diarrhea from acute gastroenteritis in the U.S. The worldwide economic burden of the illness equals about $60 billion in healthcare costs and lost productivity, according to the CDC. Even a small percentage of that lost revenue recouped by a vaccine manufacturer would produce a blockbuster.
Vaxart is betting that its bivalent vaccine pill, VXA-G1.1-NN, will be that blockbuster. To design it, the company used what Tucker called a “bag of tricks.” One of those tricks leverages a similar technology to some gene therapies: a viral vector. Vaxart packages a norovirus antigen inside a non-replicating adenovirus. That non-replicating virus also carries a double-stranded RNA load, which acts as an adjuvant to stimulate an immune response in the exact part of the body that norovirus attacks—the gut.
But using a viral vector comes with a trade-off: they’re easily destroyed by the harsh environment of the stomach and intestines, and even packaging the adenovirus into a pill can destroy it. So Vaxart perfected a gentler form of pill-making to ensure the dose survived all the way to the gut without being digested.
“We had to learn how to tablet it without crushing the biological entity,” Tucker said.
That bag of tricks has paid off in terms of clinical trial results. In a Phase 2b trial, VXA-G1.1-NN reduced infections by 30% in volunteers who were challenged with norovirus four weeks after vaccination compared to volunteers who received placebo, according to a May 2025 press release. An earlier Phase 1b study showed the vaccine generated strong immunity in mucosal linings, where the virus first enters the body. The company plans to launch a Phase 3 trial early this year, contingent upon a partnership or other funding.
Vaxart’s clinical development position puts it on track with or ahead of its competitors, which have all hit roadblocks. Takeda, for example, had long been developing an injectable norovirus vaccine made of virus-like particles. Takeda spun that candidate’s development out into a separate company called HilleVax in 2021, but the vaccine flunked a Phase 2 trial in 2024, cratering its stock.
The only other large competitor in the norovirus space is Moderna, which started dosing patients with its mRNA-based vaccine, mRNA-1403, in a Phase 3 trial in September 2024. That trial was hit with an FDA hold in February 2025 after a case of Guillain-Barré Syndrome. After the hold was lifted, the trial’s Southern Hemisphere portion struggled to find enough patients. Instead, in November 2025, Moderna shifted the trial to the north to locate more patients. And now, following a refuse-to-file (RTF) from the FDA for its flu vaccine, the future of Moderna’s mRNA-based pipeline is uncertain.
While norovirus doesn’t mutate as much as other seasonal infections, treatments like the flu vaccine could help inform Vaxart’s distribution plan. “[Flu] is a good model,” Tucker said. “We could change the strain every year if we needed to.” The goal for the company is to just to get its vaccine to the people who need it most—such as families with kids and cruise ship patrons—at the time they most need it.
“We’re going to provide protection through the worst time, which is winter for norovirus,” Tucker said. “It’s called winter vomiting disease for a reason.”
Editor’s note (Feb. 18): This article has been updated to clarify that Vaxart’s Phase 3 trial of VXA-G1.1-NN, set to begin early this year, is contingent upon a partnership or other funding.
