Phase 1b trial data demonstrated immune response, with 85% reduction in viral shedding and robust mucosal immunity in elderly adults.
Image credits: Vaxart Inc
Vaxart, Inc announced the publication of complete data from its Phase 1b trial of its first-generation oral pill norovirus vaccine candidate in elderly adults. The trial demonstrated the vaccine’s ability to induce strong antibody and T-cell responses in adults aged 55-80, a population known to experience age-related declines in immune responses to injected vaccines.1
The study showed that the vaccine-induced significant increases in serum anti-VP1 IgA and IgG antibodies, as well as VP1-specific mucosal-homing B cells. It also induced mucosal T-cell responses, which could contribute to protection against persistent infections. These immune responses were consistent across both age groups in the study.1
The Phase 1b trial included 63 participants aged 55-65 and 66-80 years. The vaccine was administered orally at three dose levels in a prime-and-boost regimen, 28 days apart. The study showed that all three dose cohorts had statistically significant increases in serum anti-VP1 IgA compared to the placebo group on days 29 and 57, with dose-dependent increases in serum anti-VP1 IgG. Additionally, the vaccine-induced mucosal IgA responses in both saliva and the nasal cavity.1
The vaccine was well-tolerated, with all reported mild to moderate adverse events. The most common side effects were headache (14%) and malaise/fatigue (16%), similar to the placebo group.1
“The immune responses observed in this study are encouraging, especially given the elderly’s increased risk of norovirus-related morbidity and their typically reduced immune responses to injected vaccines,” said James F Cummings, MD, chief medical officer at Vaxart, in the press release. “The ability of an orally administered vaccine to generate immune responses beyond the gastrointestinal tract suggests potential for broader applicability of this vaccine platform.”1
The vaccine generated a 100% increase in serum anti-VP1 IgA and a dose-dependent increase in serum anti-VP1 IgG compared to placebo.
The vaccine induced significant mucosal IgA responses in saliva and nasal cavity, with 85% reduction in viral shedding in stool.
The vaccine was well-tolerated, with mild to moderate adverse events; common side effects included headache (14%) and malaise/fatigue (16%).
Vaxart’s oral pill vaccine platform aims to overcome the limitations of traditional injected vaccines, including cold storage and needle-stick injuries. The company is advancing a second-generation oral norovirus vaccine, with a Phase 1 trial scheduled for mid-2025.1
Vaxart has previously reported that its oral norovirus vaccine reduced infection rates and viral shedding in a Phase 2 challenge study. Additionally, a Phase 1 study in lactating mothers showed a 4-6 fold increase in norovirus antibodies in breast milk, potentially offering passive protection for infants.1
In our interview at IDWeek 2024, with Sean Tucker, PhD, Vaxart’s founder and chief scientific officer we also discussed Vaxart’s efforts in developing oral vaccines for norovirus, focusing on immunogenicity, safety, and efficacy. Tucker provided insights on a study of the VXA-GI.1-NN vaccine, highlighting its safety, strong immune responses, and mucosal immunity’s importance in combating norovirus.2
Both vaccines show promise in generating significant immune responses, particularly mucosal IgA, and have demonstrated some protection against norovirus infection and reduced viral shedding. While this new update highlights early-stage findings with elderly populations, the VXA-GI.1-NN vaccine emphasizes the potential of oral administration to stimulate immunity at both systemic and intestinal levels, which is crucial for norovirus prevention. Both trials highlight the potential of Vaxart’s oral vaccine platform in preventing norovirus and may play an important role in future public health strategies.
Stay tuned for our upcoming interview with Tucker about the Phase 1b trial of Vaxart’s first-generation oral pill norovirus vaccine candidate in elderly adults.
