Scientists at Washington University School of Medicine in St. Louis are working on a nasal vaccine against COVID-19

Unlike other COVID-19 vaccines under development, this vaccine is administered through the nose, meaning it reaches the mucous membrane, which is the primary site of infection with the SARS-CoV-2 virus. This may be why it triggers a strong immune response, especially in the nose and respiratory tract, preventing the infection from spreading throughout the body.

For example, in a study on mice^[1], scientists administered the vaccine in two ways – nasally and intramuscularly. In both cases, it triggered an immune response that prevented pneumonia. However, when administered intramuscularly, it did not prevent infection in the nose and lungs, meaning that the vaccine reduced the severity of COVID-19 but did not completely block the infection, allowing it to spread in the community. At the same time, the nasal route of delivery prevented infection in both the upper and lower respiratory tract.

To develop the vaccine, researchers inserted the spike protein of the SARS-CoV-2 virus, which it uses to enter cells, inside another virus called adenovirus, which causes the common cold. But scientists have altered the adenovirus, making it unable to cause the disease. The harmless adenovirus carries the spike protein to the nose, which allows the body to build up an immune defense against the coronavirus without getting sick.

It is important that the new intranasal COVID-19 vaccine does not use live attenuated virus, which increases its safety. Another innovation used by scientists in this vaccine is two additional mutations in the spike protein that stabilize it in a certain form that is most conducive to antibody formation. Just one dose was enough to create a reliable and sustained immune response in mice. The researchers now plan to test the vaccine in non-human primates and humans to see if it is safe and effective in preventing COVID-19 infection.

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1. 1. Hassan AO, et al. A single-dose intranasal ChAd vaccine protects upper and lower respiratory tracts against SARS-CoV-2. Cell. Aug. 19, 2020. doi: 10.1016/j.cell.2020.08.026