It is the belief of several teams of scientists around the world. Covid vaccines in sprays or drops, to be taken by nose or mouth, are the real promise ahead and could change the pandemic. Some data seem to support them, although so far there is little evidence from human trials. Meanwhile, the first approvals arrive. This week the green light was given in China for the use as a booster dose of the inhalable version of a vaccine manufactured by CanSino Biologics in Tianjin.
Mucosal immunity
CanSino’s is just one of over 100 oral or nasal vaccines under development around the world, according to “Nature” reports online, citing data from Airfinity, a health industry analysis company. In recent times, companies and research groups working on new types of immunization have multiplied, based on the approach of using sprays or drops, instead of injections, to stimulate mucosal immunity (i.e. trigger the immune cells present in the thin membranes mucous membranes that line the cavities of the nose and mouth, i.e. the entrance doors of the virus) and improve protection against SARS-CoV-2, quickly stopping it before it spreads in the body.
Already in use against the flu
The hope of the scientists is that these mucosal vaccines are able to prevent even mild cases and that they block the contagion to other people, obtaining the so-called “sterilizing immunity”. Some such vaccines are already licensed for other diseases, including a spray flu vaccine. The data obtained in animals support the idea that sterilizing immunity can be induced against Covid. It would be the missing piece so far with intramuscular vaccines.
Sentinels at the site of infection
One reason is that shield injections provoke an immune response that includes T and B lymphocytes. These cells and the antibodies produced circulate through the bloodstream, but are not present in the nose and lungs at levels high enough to provide rapid protection. . In the time it takes to get there from the bloodstream, the virus spreads and the infected person gets sick. Mucosal vaccines, on the other hand, can stimulate an immune response throughout the body and also in the respiratory tract. The immune cells located here “act as sentinels at the site of infection,” according to Benjamin Goldman-Israelow, a physician-scientist at Yale School of Medicine in New Haven, Connecticut.