Successful Testing of Oral Norovirus Vaccine in Human Challenge Study

Vaxart Inc., in collaboration with various academic researchers, has evaluated the efficacy of the VXA-G1.1-NN vaccine aimed at preventing norovirus infections, in a recent human challenge trial. The study revealed that vaccinated participants experienced a 30% reduction in infection rates compared to placebo recipients, alongside lower viral shedding and elevated levels of protective antibodies both in the bloodstream and mucosal tissues.

Norovirus remains one of the primary causes of gastroenteritis globally, characterized by symptoms such as vomiting, diarrhea, and abdominal pain. Its transmission predominantly occurs through contaminated food, water, surfaces, or direct person-to-person contact. Despite extensive research, no vaccines have yet received regulatory approval for norovirus prevention, partly due to challenges in identifying reliable immune protection markers without exposing individuals to the virus.

Traditional clinical trials for vaccines generally assess efficacy in populations already infected, which is unethical and unfeasible for preventive vaccines. To address this, researchers employed a controlled human challenge model, where volunteers are intentionally exposed to the virus under clinical supervision, enabling precise measurement of infection rates and immune responses.

The study, published in Science Translational Medicine, involved 165 participants randomized evenly to receive either the oral vaccine or a placebo. Researchers monitored immune responses through various biological samples and found significant increases in norovirus-specific antibodies, including IgA and IgG, 28 days post-vaccination. These antibodies play a key role in mucosal and systemic immunity.

On day 28, participants were deliberately exposed to GI.1 norovirus. Results showed a notable decrease in infection incidence among vaccine recipients (57.1%) compared to placebo (81.5%), indicating a 30% relative reduction. Though there was a reduction in gastroenteritis cases (44.7% vs. 56.9%), it was not statistically significant. The vaccine was well tolerated, with mostly mild adverse effects like fatigue, headache, and malaise.

The findings suggest that the VXA-G1.1-NN vaccine stimulates an immune response that could provide protective benefits against norovirus. This development is particularly promising for environments with high transmission risks, offering a potential tool to curb outbreaks and improve public health measures.

Vaxart’s innovative use of human challenge models has helped identify immune markers predictive of vaccine success, potentially accelerating further development and regulatory approval processes. However, these studies require strict ethical considerations due to the deliberate exposure to pathogens.

This research marks a significant advance in norovirus vaccine development, although further clinical trials are necessary to confirm efficacy and safety before widespread use.