On Oct. 7, 2021, Vaxart announced that a Duke University-led study published in bioRxiv showed that Vaxart’s (investigational oral tablet vaccine reduced the airborne transmission of SARS-CoV-2 virus in an animal model.

These results are consistent with those from Vaxart’s Phase II human flu challenge study, which showed that Vaxart’s oral tablet vaccine was better at reducing shedding than the injectable flu vaccine comparator.

A limitation of the currently approved injected COVID-19 vaccines is that airborne transmission occurs in people who have received them. The preclinical study also demonstrated that Vaxart’s oral vaccine platform induces robust systemic and mucosal responses.

Researchers vaccinated hamsters orally or intranasally with Vaxart’s S-only vaccine candidate and then exposed them to significant levels of the COVID-19 virus to promote vaccine breakthrough. Vaccinated hamsters cleared infectious virus in the nose and lungs quickly. Before clearing the infection, the vaccinated hamsters were exposed to unvaccinated hamsters via aerosol. The mucosally vaccinated hamsters infected fewer hamsters and created less severe clinical symptoms than did unvaccinated hamsters. 

The study used a hamster infection and aerosol transmission system to study the potential impact of oral vaccination on transmission of SARS-CoV-2 to uninfected individuals.

Animals received oral, intranasal or intramuscular vaccines targeting S protein, and a control group received a mock vaccination (four animals per group). These index hamsters were then infected intranasally with a high titer of SARS-CoV-2 to replicate a post-vaccination breakthrough infection.

One day after viral challenge, index hamsters were placed upstream of unvaccinated hamsters in a chamber that allowed aerosol movement but not direct contact with other animals or bedding or feeding receptacles used by other animals. Index animals were evaluated for antibodies for systemic (IgG) and mucosal (IgA) immunity; all animals were evaluated for viral titers and body weight and lung weight (indicators of SARS-CoV-2 infection).