Norovirus (NV) is the leading cause of acute gastroenteritis worldwide, but no specific treatment currently exists for norovirus gastroenteritis (NVG). VXA-GI.1-NN is a non-replicating adenovirus-vectored thermostable oral vaccine that has been demonstrated to be safe and tolerable in clinical trials and generates strong serum and mucosal immune responses. This study aimed to evaluate the safety, immunogenicity, and protective efficacy of VXA-GI.1-NN after challenge with NV GI.1. VXA-GI.1-NN was found to be safe and well-tolerated among participants.
Dr. Sean N Tucker, Vaxart’s Vice President of Research and CSO, presented this research at IDWeek 2024. It details key findings regarding the immunogenicity and efficacy of vaccines compared to existing prophylaxis. “We found that the number of people infected with the norovirus vaccine tablets was significantly reduced, which is a great result from our perspective.” It was very important to note that the amount of norovirus present in the feces was observed to be significantly lower in the vaccine group compared to the placebo group, given the highly infectious nature of norovirus. And this discovery could have far-reaching implications.”
This vaccine induced strong serum and cellular immunogenicity, as evidenced by a significant increase in VP1 GI.1-specific antibody-secreting cells (ASC) and serum antibodies. Serum functional antibody responses measured by norovirus blocking antibody assay (NBAA) were significantly higher in the vaccine group compared to the placebo group. Additionally, VP1-specific IgA levels were significantly increased in the nasal secretions and saliva of vaccinees. The preventive effect of NVG was 21%, and the preventive effect of norovirus infection was 29%. Of note, among participants who received VXA-GI.1-NN, the geometric mean of fecal viral shedding was reduced by 85%. The combined evidence analysis across all six outcomes resulted in a Z-score of 5.56, indicating the vaccine’s protective efficacy.
Professor Tucker explains the demographic choices in this study: It was important to make sure the population was relatively healthy. Having said that, we believe that one of the main groups that will benefit from this vaccine is the elderly, who often have a compromised immune response. We have previously conducted studies in older adults, and the results showed that our vaccine elicited immune responses similar to those in younger adults, and our results are reasonable for older populations as well. It was suggested that it may be applicable. ”
In a randomized controlled trial, 165 healthy adults were divided into two groups, with one group receiving a single oral dose of VXA-GI.1-NN vaccine and the other group receiving a placebo. . Twenty-eight days after vaccination, 141 participants were exposed to specific strains of norovirus. Researchers monitored side effects for one week and tracked adverse events for 28 days after exposure. They evaluated the effectiveness of the vaccine by looking for cases of acute gastroenteritis caused by norovirus and measuring the amount of norovirus in stool and vomit samples using a specific test (qPCR). did. The immune response was assessed by measuring specific antibodies in blood and mucosal samples, and an overall analysis was performed to determine the protective efficacy of the vaccine.
“The next step is to conduct a Phase 2B study and then submit a package to the FDA to begin a Phase 3 efficacy study. One of the key advantages of our vaccine approach is , unlike traditional injectable vaccines that are effective in eliciting a serological response, our vaccine, which is delivered to mucosal surfaces through swallowing, not only produces serum antibodies but also within the intestinal lumen. It also stimulates antibodies, and because norovirus infects intestinal cells, we think these intestinal antibodies will be especially important for fighting norovirus.”
In conclusion, VXA-GI.1-NN was proven to be safe, immunogenic, and effectively reduce both postchallenge viral shedding and norovirus (NV) infection. The tabletted VXA-GI.1-NN vaccine may help alleviate the epidemic by reducing viral shedding. A comprehensive analysis of the evidence provides strong statistical signals supporting the protective efficacy of vaccines and suggests that vaccines may play an important role in public health strategies against norovirus outbreaks.
Reference A Phase 2, double-blind, placebo-controlled study shows that oral tablet norovirus vaccine VXA-G1.1-NN is immunogenic, efficacious, and reduces viral shedding after norovirus challenge. Poster #220 presented at IDWeek 2024. October 16-19, 2024, Los Angeles, California.
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