Next-generation COVID-19 vaccines targeting the virus's entry points—the nose and mouth—might achieve what traditional vaccines cannot: limiting the spread of respiratory infections by preventing their transmission.

This conclusion comes from a new study by researchers at Washington University School of Medicine in St. Louis, published in the journal "Science Advances." Using a nasal vaccine approved for use in India and further developed in the US, researchers found that vaccinated hamsters with infections had viral levels in their airways 100 to 100,000 times lower than those that received the injectable vaccine or were unvaccinated.

Additionally, the researchers discovered that hamsters that received the nasal vaccine did not transmit the virus to others, effectively breaking the cycle of transmission. In contrast, an approved injectable vaccine failed to prevent the spread of the virus.

The researchers emphasize that mucosal vaccines, sprayed into the nose or inhaled through the mouth, might be key to controlling respiratory infections like flu and COVID-19, which continue to spread and cause illness and death. “To prevent transmission, you need to keep the amount of virus in the upper airways at low levels,” says lead author Jacob Boone, professor of Medicine, Molecular Microbiology, Pathology, and Immunology.

“The less virus there is in the first place, the lower the chance you will infect someone else if you cough, sneeze, or even just breathe near them. This study shows that mucosal vaccines are superior to injectable vaccines in limiting virus replication in the upper airways and preventing its spread to the next person. In an outbreak or pandemic situation, this is the kind of vaccine we would want,” Boone adds.

It is noted that a team of researchers at Washington University, including Boone, is working on developing a nasal vaccine for avian flu.