New Duke University-led Study Shows That Vaxart's Oral COVID-19 Vaccine Candidate Reduces Airborne Transmission of SARS-CoV-2 Infection in Animal Model
These results are consistent with those from
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
Researchers vaccinated hamsters orally or intranasally with
"These findings show that our vaccine candidate can reduce transmission of SARS-CoV-2, even when there is infection breakthrough in vaccinated subjects," said Dr.
"Existing injected vaccines don't always protect against viral shedding and transmission to other people. A vaccine that reduces shedding and reduces the probability of infection could make a big difference in protecting lives and public health, particularly given the large number of unvaccinated individuals. This study used the same vaccine candidate
Earlier this week,
The mucosal surface of the upper respiratory tract is the initial site of SARS-CoV-2 replication and the primary site of infection. Vaccines that induce robust mucosal immune responses may have the greatest impact on reduction of SARS-CoV-2 transmission. Approved COVID-19 vaccines, all of which are administered via intramuscular injection, stimulate systemic immune responses but have minimal effects on mucosal immunity.
About the Study
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).
Key findings from the study include:
- Oral and intranasal vaccination against S protein induced robust systemic and mucosal antibody responses.
- Post-vaccination, the oral and intranasal groups had higher serum IgG and IgA, as well as higher bronchoalveolar lavage (BAL) IgA compared to control animals.
- Oral and intranasal vaccination accelerated clearance of SARS-CoV-2 RNA and protected animals against disease.
- Following intranasal delivery of SARS-CoV-2 and detection of substantial amounts of viral RNA in nasal swabs, vaccinated hamsters had decreased viral RNA and infectious virus in the nose and lungs and experienced less lung pathology (determined by lung weight) and lost less weight (a characteristic of SARS-CoV-2 disease in hamsters) compared to mock-vaccinated hamsters post challenge.
- Oral and intranasal vaccination limited transmission of SARS-CoV-2 to unvaccinated animals.
- Unvaccinated animals exposed to animals vaccinated orally or intranasally shed lower nasal swab viral RNA than animals receiving intramuscular or mock vaccinations.
- Taken together, these data demonstrate that oral immunization against SARS-CoV-2 S protein resulted in reduced disease and decreased SARS-CoV-2 transmission in a hamster model.
Vaxart is a clinical-stage biotechnology company developing a range of oral recombinant vaccines based on its proprietary delivery platform. Vaxart vaccines are designed to be administered using tablets that can be stored and shipped without refrigeration and eliminate the risk of needle-stick injury. Vaxart believes that its proprietary tablet vaccine delivery platform is suitable to deliver recombinant vaccines, positioning the company to develop oral versions of currently marketed vaccines and to design recombinant vaccines for new indications. Vaxart's development programs currently include tablet vaccines designed to protect against coronavirus, norovirus, seasonal influenza, and respiratory syncytial virus (RSV), as well as a therapeutic vaccine for human papillomavirus (HPV), Vaxart's first immune-oncology indication. Vaxart has filed broad domestic and international patent applications covering its proprietary technology and creations for oral vaccination using adenovirus and TLR3 agonists.
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