Norovirus Vaccine: Is There One? Trial Status in 2026

There is no norovirus vaccine yet. As of October 14, 2026, no vaccine against norovirus is approved in the United States, and we found none licensed anywhere else. The candidate furthest along, Moderna's mRNA-1403, is in a large Phase 3 trial that did not meet its bar for early success at an interim analysis reported on July 31, 2026; the trial remains blinded and is being extended through another winter. There is also no approved antiviral drug for norovirus. For now, prevention still means soap, water, bleach, and staying home when sick.

This page explains where each vaccine candidate stands, why norovirus has been so hard to vaccinate against, and what to watch for next. It is part of our norovirus symptoms guide.

Is there a vaccine for norovirus?

No. The CDC's travel medicine reference states that no norovirus vaccine or antiviral agents are currently available. Companies developing vaccines said the same in their 2026 financial reports. A flu shot does not protect against norovirus, because "stomach flu" is not influenza. The rotavirus vaccine that babies receive protects against rotavirus, a different stomach virus, and not against norovirus.

Norovirus vaccine candidates at a glance

Candidate (developer)	Type	Stage	Status as of October 2026
mRNA-1403 (Moderna)	mRNA, one injection; three genotypes (GII.4, GI.3, GII.3)	Phase 3 in adults	Interim analysis on July 31, 2026 did not meet criteria for early success; trial continues, blinded, with an added cohort
mRNA-1405 (Moderna)	mRNA; five genotypes	Phase 1/2	In early testing; no results or Phase 3 plans announced
Oral tablet vaccine (Vaxart)	Pill; viral vector	Phase 1 and Phase 2 completed	Next trial depends on a partner or funding, the company says
HIL-214 (HilleVax, originally Takeda)	Virus-like particle injection; two genotypes	Phase 2b in infants	Failed in 2024; infant development stopped; company acquired in 2025
Quadrivalent recombinant vaccine (Anhui Zhifei Longcom, China)	Protein-based injection; four genotypes	Phase 3 in children in China	Ongoing; primary completion estimated March 2027
Bivalent GI.1/GII.4 vaccine (National Vaccine and Serum Institute, China)	Protein-based injection	Phase 3 in children in China	Listed as completed in the trial registry; no results published that we could find
INT101 (InThera, South Korea)	Three genotypes including GII.17	Phase 1	Began August 2026

Sources: company statements filed with the Securities and Exchange Commission, ClinicalTrials.gov records, and published papers, listed below.

Moderna's mRNA-1403: the closest, and not there yet

Moderna's candidate uses the same messenger RNA approach as its COVID-19 vaccine. It carries instructions for the outer shell protein of three norovirus genotypes: GII.4, GI.3, and GII.3. In early-stage trials the company reported that it was generally safe and well tolerated and produced immune responses in both younger and older adults.

The Phase 3 trial

The Phase 3 study, called Nova 301, began in September 2024. It is a randomized, placebo-controlled trial in adults 18 and older, with an emphasis on people 60 and older, in which each participant gets a single injection. According to its ClinicalTrials.gov record, it has enrolled 37,864 people at 283 sites in the United States, Puerto Rico, Canada, the United Kingdom, Japan, Australia, and Panama. The main question is whether the vaccine prevents moderate or severe gastroenteritis caused by the norovirus genotypes it contains.

What has happened so far

Date	Development
September 2024	Phase 3 trial starts
February 14, 2025	Moderna discloses the trial is on FDA clinical hold after a single report of Guillain-Barré syndrome in a participant, under investigation
May 1, 2025	Moderna reports the FDA has lifted the hold
November 6, 2025	Too few cases of illness have occurred to analyze results; trial extended into a second winter (2025-26)
July 31, 2026	Interim analysis: the study "did not meet statistical criteria for early success"; trial continues, blinded, with plans to enroll an additional cohort

That last line needs careful reading. A vaccine trial like this one waits for a set number of participants to get sick, then compares the vaccine and placebo groups. An interim analysis is an early look that can stop a trial ahead of schedule if the benefit is overwhelming. Missing that early bar is not the same as a final result showing the vaccine does not work, and Moderna has not released any efficacy figure. It is also not good news: some financial and trade publications described it as a miss. The accurate summary is that nobody outside the trial's independent monitors knows yet whether mRNA-1403 works.

Moderna's president, Stephen Hoge, told investors on July 31, 2026 that cases counting toward the main result had come in more slowly than expected, in part because the first season featured "a unique outbreak of a different set of strains of norovirus" that did not count toward the primary endpoint. He did not name the strains. CDC surveillance shows that in the 2024-25 season a genotype called GII.17, which is not in the vaccine, caused about 75 percent of typed U.S. outbreaks. By 2025-26, GII.4, which is in the vaccine, was again the most common. Hoge said the company expects to run the trial for one more season, the winter of 2026-27.

When could results come?

Moderna has not given a date for the final analysis. The trial registry lists an estimated completion date of February 15, 2027, in an entry last updated in May 2026, before the company announced the additional cohort. What Moderna has said is that the study remains blinded, that it needs additional cases from a further cohort, and that it expects to run the trial for one more season, the winter of 2026-27. If the results were positive, the company would still need to file for FDA approval, the agency would need to review the data, and the CDC's vaccine advisory process would have to decide who should get it. Because the trial itself is set to run through the 2026-27 winter, no norovirus vaccine will be available this season. Moderna's July 31 release lists an Analyst Day on November 12, 2026.

Vaxart's oral tablet

Vaxart, a California company, is developing a vaccine taken as a pill. The idea is appealing for a gut infection, because a tablet can stimulate immune defenses in the intestinal lining itself.

In a Phase 2b study, 165 healthy adults received the tablet or a placebo and were then deliberately exposed to a norovirus under controlled conditions. Results, published in Science Translational Medicine in 2025, showed a 30 percent relative reduction in infection in the vaccine group, which was statistically significant. The reduction in actual gastroenteritis was 21 percent and was not statistically significant. In other words, a signal, but a modest one.

The company has since tested redesigned, second-generation versions in a small Phase 1 trial and reported stronger antibody responses than with the original. In its report for fiscal 2025, Vaxart said it planned to start its next norovirus trial in 2026 "pending a partnership or other funding." We could not confirm that such a trial has begun.

HilleVax: the infant trial that failed

HIL-214, a virus-like particle vaccine first developed by Takeda, was tested in about 2,800 infants in the United States and Latin America. In July 2024 HilleVax announced that the trial had failed: there were 25 cases of moderate or severe norovirus gastroenteritis among vaccinated infants and 26 in the placebo group, for an efficacy of 5 percent, with a confidence interval that ran from minus 64 to 45 percent. No benefit showed up on secondary measures either. The company stopped development in infants, and in September 2025 it was acquired by XOMA Royalty. We found no active trials of its norovirus vaccines in 2026.

The result mattered beyond one company, because young children are among those who would benefit most from a vaccine, and this was the first efficacy trial in that age group.

Why is a norovirus vaccine so hard to make?

• There are many noroviruses. The CDC classifies them into 10 genogroups and roughly 48 genotypes. Infection with one type may not protect against others, so a vaccine has to cover several and still may miss what circulates in a given winter.
• The dominant strain changes. Between 2002 and 2012, new variants of GII.4 emerged every two to four years. GII.4 Sydney then led for more than a decade, until GII.17 surged in 2024-25. A vaccine is built around specific genotypes chosen years ahead; Moderna said strains that did not count toward its trial's main result slowed the collection of cases in the first season.
• Immunity fades. The CDC says it is not known exactly how long protection after infection lasts. Volunteer studies have suggested as little as two months to two years; a modeling study in Emerging Infectious Diseases estimated about four to nine years. A vaccine may need boosters.
• The virus was almost impossible to grow in the lab. For decades scientists could not culture human norovirus in cells, which slowed basic research. That changed in 2016, when a team reported in Science that it had grown the virus in miniature intestinal tissue derived from human stem cells.
• There is no simple blood marker of protection. Researchers lack an agreed immune measurement that reliably predicts whether a vaccinated person is protected, so every candidate has to prove itself in large, slow trials that wait for people to get sick.
• The illness is brief. Because most people recover in one to three days, a vaccine has to be very safe and reasonably priced to be worth giving widely.

Who would be likely to get a vaccine first?

No official recommendation exists, since nothing is licensed. But the design of the trials shows where developers are aiming. Moderna built its Phase 3 study around adults 60 and older, the group that accounts for most of the roughly 900 norovirus deaths in the United States each year. Researchers writing about vaccine strategy have named these groups as likely priorities:

• Adults 65 and older, especially residents of nursing homes, where more than half of U.S. norovirus outbreaks occur
• Young children, who account for most norovirus-related doctor and emergency visits
• People with weakened immune systems
• Health care workers and food handlers
• Military personnel and travelers, including cruise passengers

The burden behind that interest is large: the CDC estimates 19 to 21 million illnesses, 109,000 hospitalizations, and 465,000 emergency department visits from norovirus in the United States each year. Worldwide, the World Health Organization estimates about 200,000 deaths annually, including 50,000 among children.

Is there any medicine that treats or prevents norovirus?

No approved one. The CDC says there is no specific medicine to treat norovirus illness, and antibiotics do not help because they act on bacteria, not viruses.

• Nitazoxanide, an antiparasitic drug, shortened symptoms by about a day in a small 2006 trial that included people with norovirus, rotavirus, or adenovirus; the study's lead author worked for the drug's maker. In a National Institutes of Health-sponsored trial in transplant recipients with chronic norovirus, published in 2026, it did not shorten symptoms or viral shedding. It is not FDA-approved for norovirus.
• CDI-988, an experimental antiviral pill from Cocrystal Pharma, is in an early-stage study in which volunteers are deliberately exposed to norovirus. The company said in September 2026 that it expects preliminary results near the end of 2026 or in early 2027.

Treatment today is supportive: fluids, rest, and watching for dehydration. See norovirus treatment.

What actually works now

Until a vaccine arrives, these measures, all from the CDC, do the work:

1. Wash hands with soap and water for at least 20 seconds. Hand sanitizer does not work well against norovirus.
2. Stay home, and do not prepare food or care for others, until 48 hours after symptoms stop.
3. Disinfect contaminated surfaces with a bleach solution of 5 to 25 tablespoons per gallon of water, or a product on the EPA's List G. Instructions are in how to kill norovirus.
4. Wash soiled laundry hot, on the longest cycle, and dry on high heat.
5. Cook shellfish to at least 145°F, and rinse fruits and vegetables.

To see whether the virus is active where you live this season, check current norovirus outbreaks.

Can I join a norovirus vaccine trial?

Possibly. Moderna has said it plans to enroll an additional group of participants for the 2026-27 season, though it has not published the size or locations. Open studies are listed on ClinicalTrials.gov; search for "norovirus vaccine" and filter by "recruiting" and your state. Participation is voluntary, half of participants in a placebo-controlled trial do not receive the vaccine, and you should discuss any trial with your own doctor first.