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Phase 1b trial data demonstrated immune response, with 85% reduction in viral shedding and robust mucosal immunity in elderly adults.



Vaxart Phase 1b Trial Shows 100% Increase in Serum Anti-VP1 IgA in Elderly Adults with Oral Norovirus Vaccine

Prashant Kumar’s study on indoor air quality aboard cruise ships highlights the critical role of ventilation and masking in reducing infection risks.

Enhancing Air Quality and Controlling Infections on Cruise Ships

Sasirekha Ramani, PhD, discusses the potential of 2′FL as a treatment for norovirus and what more research could reveal.

Human Milk Sugar Blocks Norovirus in Lab Models

Vaxart enrolled its first participants for its dose-ranging and boosting regimen studies.

Norovirus Oral Tablet Vaccine Enters Phase 1b Trials 

Investigators in Tennessee detailed associations between seasonal increases in sporadic pediatric cases of norovirus gastroenteritis and reported norovirus outbreaks among older populations.

Sporadic Pediatric Norovirus Cases May Predict Broader Outbreaks

Sean Tucker , PhDhighlights effective immune response and mucosal immunity, paving the way for broader applications in viral disease prevention.

Vaxart's Oral Norovirus Vaccine: Key Study Findings and Future Plans

Vaxart, Inc recently published complete data from its phase 1b trial of its first-generation oral norovirus vaccine, demonstrating encouraging results in elderly adults. The study showed that the vaccine was capable of inducing strong antibody and T-cell responses in adults aged 55-80 years, a group known to experience weakened immune responses to traditional injectable vaccines. The vaccine triggered significant increases in serum anti-VP1 IgA and IgG antibodies and mucosal T-cell responses, with no significant differences observed between the older adults and younger populations previously studied.

In our interview with Sean Tucker, PhD, chief scientific officer at Vaxart, he spoke about the study and its implications, explaining that, "From the standpoint of a reference point, many injectable vaccines are known to work less efficiently in older adults, and the way that these have been souped up to make them work better is to add more antigen or an adjuvant. And what we wanted to know in this study [was], can we see whether our vaccine works well in the older population? And the good news, from our standpoint, is that there didn't seem to be any differences in the immune responses we got compared to what we'd seen in prior studies in younger adults." This finding suggests that the oral vaccine may not require significant adjustments to be effective in elderly adults.

The study also revealed that although the vaccine is designed to target the intestine, it was effective in generating antibody responses not only in the intestinal tract but also in the nose and mouth—areas potentially crucial for protecting against respiratory infections. "While this vaccine is designed to go into the intestine, we also saw some really great increases in antibody responses in the nose and the mouth, which could be even more important for things like COVID or flu, where pathogens usually invade through the nose," Tucker said. This mucosal immunity could have broader applications, particularly in preventing the transmission of respiratory viruses.

Looking ahead, Vaxart is progressing to second-generation norovirus vaccine candidates. Tucker revealed that the company is already working on these candidates, which have shown improved immunogenicity in animal models. The company plans to move these forward into clinical trials, with data expected by mid-2025. "Our expectation, of course, is that these new candidates will do much better, and our plan is to push it forward into late-stage trials after that," Tucker added.

Vaxart's oral vaccine platform is designed to overcome challenges associated with traditional vaccines, including cold storage and needle-stick injuries. With recent outbreaks of norovirus across the country, Tucker addressed the potential for the vaccine to reduce transmission. He explained, "One of the big advantages of our vaccine candidate is that it should do a better job of protecting against getting the virus. We've shown in a norovirus challenge study that our vaccine was able to suppress the amount of virus that was actually being secreted. This could be really important for blocking or inhibiting transmission, even in cases of breakthrough infections."

As the company moves forward with its second-generation vaccines, Vaxart's innovative oral platform could play a key role in not only preventing norovirus infections but also potentially offering protection against other viral diseases through mucosal immunity.

Flitter BA, Greco SN, Lester CA, et al. An oral norovirus vaccine tablet was safe and elicited mucosal immunity in older adults in a phase 1b clinical trial. 

. 2025;17(788):eabc1234. doi:10.1126/scitranslmed.abc1234

Sean Tucker, PhD, highlights effective immune response and mucosal immunity, paving the way for broader applications in viral disease prevention.

Sasirekha Ramani, PhD  on creating a broad-spectrum antiviral that could be effective in various clinical settings, especially given the emergence of new and more dominant strains.

Developing a Broad-Spectrum Treatment for Norovirus: Addressing Multiple Strains

 suggests that 2′-fucosyllactose (2′FL), a sugar found in human breast milk, may provide a new treatment for human norovirus (HuNoV), a leading cause of gastroenteritis. The study focused on the GII.4 Sydney [P16] strain of HuNoV and found that 2′FL could block the virus from entering and replicating in lab-grown human intestinal models.

In an exclusive interview with Sasirekha Ramani, PhD, a key researcher in the study, she discussed the ongoing efforts to develop a sugar-based treatment for norovirus. She explained that while the GII.4 strain has been the dominant strain of norovirus for about a decade, there has been a recent surge in outbreaks and hospitalizations, potentially linked to a new strain that has emerged and overtaken the older one.

"We definitely want to approach this from the perspective of: will this work against a broad array of strains?" Ramani explained. "Because unless you're at a large academic medical center, you typically don’t know which specific strain a person has—just whether or not they have norovirus. You’d want something that would be effective against multiple strains."

"These mini gut models are a really cool tool to study it. They’ve only been published in the last 10 years, but before that, the only way to study norovirus was by conducting controlled human infection studies," she said. "We have controlled human infection studies for three different strains of norovirus, so we could go from the lab to controlled human infection studies to determine dosing and other parameters."

Ramani emphasized that this research is still in its early stages but that the novel approach—targeting the virus's biology rather than just viral enzymes like proteases or polymerases—holds great potential. She also noted the encouraging results from testing 2′FL in organoid models made from cells of different individuals. "One of the exciting things we were able to do was test it in organoids from the same person, but from different segments. This way, we could eliminate host genetics as a factor and just focus on which segment of the gut the virus replicates in. The nice thing is, it worked across all segments."

Despite these promising results, Ramani acknowledged there is still work to be done. "Even though we tested it in 10 different organoid lines—from 10 different people—it did not completely inhibit the virus replication in every person. So, there’s more to be done."

Listen to the first part of our interview, Ramani explained that 2′FL effectively reduced norovirus replication in older children and adults but not in infants, due to lower levels of key sugars in their cells. She highlighted its novel mechanism as a "decoy receptor," blocking the virus from binding to human cells and offering a potential new approach to antiviral treatments, especially for vulnerable populations: 

https://www.contagionlive.com/view/human-milk-sugar-blocks-norovirus-in-lab-models

Patil K, Ayyar BV, Hayes NM, Neill FH, Bode L, Estes MK, Atmar RL, Ramani S. 0. 2′-Fucosyllactose inhibits human norovirus replication in human intestinal enteroids. J Virol 0:e00938-24

Advances in Mini Gut Organoid Models Reveal Key Insights into Norovirus Replication

Sean N. Tucker, PhD, highlighted that VXA-GI.1-NN demonstrated promising safety and efficacy in reducing norovirus infections, marking a potential treatment in prevention for a diverse range of demographics.

Norovirus Vaccine VXA-GI.1-NN: Oral Vaccine for Gastroenteritis Prevention

Norovirus (NV) is a leading cause of acute gastroenteritis globally, yet no specific therapy currently exists for norovirus gastroenteritis (NVG). VXA-GI.1-NN is a nonreplicating adenovirus-vectored thermostable oral vaccine that has demonstrated safety and tolerability in clinical trials, generating robust serum and mucosal immune responses. This study aimed to evaluate the safety, immunogenicity, and protective efficacy of VXA-GI.1-NN following challenge with NV GI.1. VXA-GI.1-NN was found to be safe and well tolerated among participants.

Sean N Tucker, PhD, CSO, VP of Research at Vaxart, presented this study at IDWeek 2024. e elaborates on the key findings regarding the vaccine's immunogenicity and efficacy compared to existing prevention methods. “We found a substantial decrease in the number of individuals infected with the norovirus vaccine tablet. From our standpoint, this was a wonderful result. Additionally, it was very important to note that because norovirus is easily transmitted, we observed that the amount of norovirus present in the vomit and feces of those challenged was significantly lower in the vaccine group compared to the placebo group. Given that norovirus is highly infectious, this finding could have broad implications.”

The vaccine induced strong serum and cellular immunogenicity, evidenced by substantial increases in VP1 GI.1-specific antibody-secreting cells (ASC) and serum antibodies. Serum functional antibody responses, as measured by the 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 nasal secretions and saliva of those who received the vaccine. The protective efficacy for preventing NVG was 21%, while the efficacy for preventing norovirus infection was 29%. Notably, there was an 85% reduction in geometric mean viral shedding in stool among participants who received VXA-GI.1-NN. A totality of evidence analysis across all six outcomes yielded a z-score of 5.56, indicating a protective benefit of the vaccine.

Tucker explains the demographic choice for the study, noting, “We used adults aged 18 to 49. They needed to be very healthy, as we were administering large amounts of the virus. It was crucial to ensure the population was relatively healthy. That said, we believe one of the main groups that would benefit from this vaccine is the elderly, who often have diminished immune responses. We previously conducted a study with the elderly that showed our vaccine elicited immune responses similar to those in younger individuals, suggesting the results could be reasonably applicable to an older population.”

In a randomized controlled trial, 165 healthy adults were split into two groups: one received a single oral dose of the VXA-GI.1-NN vaccine, and the other received a placebo. 28days after vaccination, 141 participants were exposed to a specific strain of norovirus. Researchers monitored for side effects for one week and tracked any adverse events for 28 days following exposure. They assessed 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). Immune responses were evaluated by measuring certain antibodies in blood and mucosal samples, and an overall analysis was conducted to determine the vaccine’s protective effect.

“As for the next steps, we are planning to conduct a phase 2b study and subsequently submit a package to the FDA to initiate phase 3 efficacy trials. One of the key advantages of our vaccine approach is that it comes in tablet form, differing from traditional injected vaccines, which are effective at generating serum responses. Our vaccine, delivered to the mucosal surface through swallowing, stimulates not only serum antibodies but also antibodies in the intestinal space. We believe these intestinal antibodies will be particularly important for combating norovirus, as it infects intestinal cells.”

In conclusion, VXA-GI.1-NN was demonstrated to be safe and immunogenic, effectively reducing both viral shedding and norovirus (NV) infection following challenge. The tableted VXA-GI.1-NN vaccine may help mitigate outbreaks by lowering viral shedding. The totality of evidence analysis indicated a strong statistical signal supporting the vaccine's protective effect, suggesting that it could play a vital role in public health strategies against norovirus outbreaks.

A Phase 2 Double-Blind, Placebo-Controlled Study Showing Oral Tableted Norovirus Vaccine VXA-G1.1-NN is Immunogenic, Efficacious, and Reduces Viral Shedding Following Norovirus Challenge. Poster #220 presented at IDWeek 2024. October 16-19, 2024. Los Angeles, CA.

Sean N Tucker, PhD, highlighted that VXA-GI.1-NN demonstrated safety and efficacy in reducing norovirus infections, marking a potential treatment in prevention for a diverse range of demographics.

Conferences

Oral Norovirus Gastroenteritis Vaccine VXA-GI.1-NN Shows Efficacy

Dorothy McCoy, PharmD, BCPS-AQ ID, Clinical Associate Professor at the Ernest Mario School of Pharmacy at Rutgers University and Clinical Pharmacist, Infectious Diseases Hackensack University Medical Center shares advice on when a patient with norovirus should go to the emergency room.

Dorothy McCoy, PharmD, shares advice on when a patient with norovirus should go to the emergency room.

When Should a Norovirus-Infected Patient Go To the Emergency Room?

Dorothy McCoy, PharmD, BCPS-AQ ID, Clinical Associate Professor at the Ernest Mario School of Pharmacy at Rutgers University and Clinical Pharmacist, Infectious Diseases Hackensack University Medical Center provides advice for healthcare practitioners on counseling patients with norovirus.

Dorothy McCoy, PharmD, provides advice for healthcare practitioners on counseling patients with norovirus.

How to Counsel Patients Who Are Infected with Norovirus

Dorothy McCoy, PharmD, BCPS-AQ ID, Clinical Associate Professor at the Ernest Mario School of Pharmacy at Rutgers University and Clinical Pharmacist, Infectious Diseases Hackensack University Medical Center 

describes what healthcare professionals can do in the event of a norovirus outbreak.

Dorothy McCoy, PharmD, describes what healthcare professionals can do in the event of a norovirus outbreak.

What Can Healthcare Providers Do in the Event of a Norovirus Outbreak?

Dorothy McCoy, PharmD, BCPS-AQ ID, Clinical Associate Professor at the Ernest Mario School of Pharmacy at Rutgers University and Clinical Pharmacist, Infectious Diseases Hackensack University Medical Center, explains why the norovirus spreads so efficiently.

Dorothy McCoy, PharmD, Clinical Associate Professor at the Ernest Mario School of Pharmacy at Rutgers University, explains why the norovirus spreads so efficiently.

Norovirus

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