They are designed to generate broad and durable immune responses, including mucosal and systemic responses. The oral route of administration provides a more efficient and convenient method of administration relative to injectable vaccines. Vaxart oral recombinant vaccines are formulated as tablets that are enterically coated for efficient delivery to the small bowel. The enteric coating protects the active ingredient from the acidic environment in the stomach. By targeting the small bowel, the vaccines engage the finely-tuned immune system of the gut to generate broad systemic and mucosal immune responses for robust, persistent immunity. Vaxart’s VAAST™ delivery platform employs a modular approach using a replication-incompetent adenovirus type 5 (Ad5) vector that delivers two payloads to the cells of the mucosal epithelium of the small bowel. One payload is the gene coding for the selected pathogen-specific protein antigen. The other payload, which is always co-delivered, is the gene coding for the Toll Like Receptor-3 (TLR-3) agonist, an adjuvant that activates the innate immune system, and was selected for its ability to stimulate broad immune responses. Every vaccine contains the TLR-3 adjuvant component. Vaxart, a San Francisco-based biotechnology company, is testing a tablet-form Covid-19 vaccine to tackle storage temperature problems, which affect even rich countries like the US, said founder Sean Tucker. “If it turns out that we will need to vaccinate people every year, it’s going to be a real challenge,” he added. “A tablet vaccine like ours … we dream that it’s going to be sent by mail, or even drone or some other delivery service, because it is room temperature stable, so you don’t have to deal with the problems with the cold-chain [infrastructure].” Targeting mucosal tissues has the potential to produce so-called “sterilising immunity”, the complete elimination of infection in the body, reducing transmission
“With the intramuscular and systemic vaccines, we know that you can often prevent or reduce the severity of disease but it’s almost never the case that you completely stop the shedding of the virus or pathogen from the site of infection,” said Chiu.