A way to prevent norovirus, the main culprit of food poisoning during winter, has opened up. Every year, 700 million people around the world are infected with norovirus and 200,000 die, but until now, there has been no preventive vaccine.
U.S. biotechnology company Vaxart announced the results of its phase 2 clinical trial of an oral vaccine that can prevent norovirus infections on the 14th (local time) in the international journal Science Translational Medicine.
Norovirus infects people through food and causes gastroenteritis. It is considered a major cause of winter food poisoning as it can survive even at a low temperature of minus 20 degrees Celsius. Symptoms include diarrhea, vomiting, abdominal pain, and fever, and it is highly contagious, capable of causing infection with even a small amount of viral particles, regardless of age. In South Korea, the number of infected cases recorded in January and February was the highest in the past 10 years, becoming a serious issue.
According to the World Health Organization (WHO), 700 million people are infected with norovirus every year, but not a single vaccine has been developed yet. The difficulty in culturing the virus, as well as the many genotypes and rapid mutations, have resulted in no successful vaccine development. In February, the U.S. company Moderna's vaccine, which had garnered high expectations, also showed serious side effects in the final phase 3 trials, leading the U.S. Food and Drug Administration (FDA) to force the halt of clinical trials.
Vaxart's oral vaccine began to attract attention after proving its efficacy and safety in phase 1 clinical trials in March. Vaxart developed the oral vaccine candidate 'VXA-G1.1-NN' by inserting the gene that makes the protein shell of the most common GⅠ.1 genotype norovirus into a harmless adenovirus vector. When the vaccine is administered, the norovirus genes emerge in the small intestine, producing antigen proteins and inducing an immune response where the body creates antibodies against it.
The research team conducted phase 2 clinical trials by dividing participants into two groups: the oral vaccine group (86 people) and the placebo group (79 people). The placebo used was Sanofi's influenza vaccine, Fluzone. After 28 days, participants were administered the most common GⅠ.1 strain of norovirus.
The oral vaccine had a 30% higher infection prevention effect than the placebo. The trial results confirmed that 57.1% of the participants in the oral vaccine group and 81.5% in the placebo group were infected with norovirus. The proportion of participants who were not infected with norovirus and showed no symptoms of acute gastroenteritis (AGE) was 34.2% in the oral vaccine group and 15.3% in the placebo group.
The vaccine increased antibodies against norovirus while reducing the virus. The research team collected samples including nasal mucus, saliva, serum, and stool from participants at various stages before and after vaccination to assess antibody activity. It was confirmed that, 28 days post-vaccination, antibodies against norovirus, including immunoglobulin G (IgG), had increased in the participants' serum. The IgG levels in the oral vaccine group were 8.76 times higher than those in the placebo group. The amount of norovirus found in samples after vaccination was also lower in the oral vaccine group.
The research team noted that "the oral norovirus vaccine triggered a strong immune response in the nasal mucosa," and that "its potential as a safe and effective oral norovirus vaccine has been proven." During the week following the vaccination, adverse reactions were reported in 58.1% of the VXA-G1.1-NN group, but most were confirmed to be mild, including lethargy and fatigue.
Becca Flitter, head of immunology at Vaxart and leader of the study, said, "VXA-G1.1-NN is manufactured as a temperature-controlled tablet, reducing the need for specialized infrastructure or skilled doctors for vaccine administration, making rapid distribution easier," and that "the oral vaccine fulfilled the safety and antibody and immune indices as well as its effectiveness."
The research team stated that phase 3 trials will use immune indices for efficacy evaluation instead of comparing infection rates after viral administration. They also mentioned that they would accelerate the development of the next generation of oral vaccines. The oral vaccine that has yielded clinical trial results is designed to target only one type of GⅠ.1 norovirus. Vaxart is also developing a bivalent vaccine to cover both GⅠ.1 and GⅡ.4 types.
References
Science Translational Medicine (2025), DOI: https://doi.org/10.1126/scitranslmed.ads0556
Science Translational Medicine (2025), DOI: https://doi.org/10.1126/scitranslmed.ads8214