New-generation Covid-19 vaccines that target the virus’ entry points, namely the nose and mouth, may do what traditional vaccines can’t: To limit the spread of respiratory infections by preventing their transmission.

That’s according to a new study by researchers at Washington University School of Medicine in St. Louis, published in the journal “Science Advances”. Using a nasal vaccine, which is approved for use in India and is being further developed in the US, the researchers found that vaccinated hamsters that developed infections had levels of the virus in their airways 100 to 100,000 times lower than those that had received the injected vaccine or they had not been vaccinated.

They also found that hamsters that had received the nasal vaccine did not transmit the virus to others, breaking the cycle of transmission. In contrast, an approved vaccine given by injection failed to prevent the spread of the virus.

The researchers point out that mucosal vaccines, which are sprayed into the nose or inhaled through the mouth, may be the key to controlling respiratory infections such as influenza and Covid-19 that continue to spread and cause illness and death. “To prevent transmission, you have to keep the amount of virus in the upper airways low,” says lead author Jaco Boone, professor of Medicine, Molecular Microbiology, Pathology and Immunology. “The less virus that’s there in the first place, the less likely you are to infect someone else if you cough or sneeze or even just breathe on them. This study shows that mucosal vaccines are superior to injectable vaccines in limiting viral replication in the upper airways and preventing spread to the next person. In an epidemic or pandemic situation, this is the kind of vaccine we would want,” he adds.

It is noted that a group of researchers at the University of Washington, including Boone, is working to develop a nasal vaccine for bird flu.