The animal trials are showing stunning success.
A new nasal vaccine for COVID-19 appears to have a unique advantage over traditional injectable vaccines: it can prevent the virus from spreading between individuals. Research published on July 31 in Science Advances demonstrates that hamsters vaccinated with this nasal spray did not transmit the virus to others, effectively breaking the chain of infection.
This study suggests that vaccines delivered via the nose or mouth could be crucial in controlling the spread of respiratory illnesses like influenza and COVID-19. Senior researcher Jacco Boon, a professor at Washington University School of Medicine in St. Louis, explained that to curb transmission, it’s essential to minimize the viral load in the upper respiratory tract. Lower viral levels reduce the likelihood of spreading the virus through actions such as coughing or sneezing. Boon noted that mucosal vaccines are more effective than injectable ones at limiting viral replication in the upper airways and preventing further transmission.
While early COVID-19 vaccines were successful in reducing severe illness and death, they were less effective at preventing transmission. In contrast, viruses such as flu, COVID-19, and RSV replicate rapidly in the nose, facilitating their spread through respiratory droplets. Injectable vaccines, being less effective in the nasal area, leave it relatively vulnerable.
Researchers have long posited that nasal or oral vaccines could reduce transmission by targeting the immune response directly in the areas most affected by these viruses. In this study, the efficacy of a nasal COVID vaccine used in India was compared with the injectable Pfizer vaccine using hamsters, which are more suitable for studying virus transmission than mice.
After allowing the vaccinated hamsters to build up their immune response, the researchers infected a separate group of hamsters and placed them with the vaccinated ones. The results showed that the nasal vaccine significantly reduced the viral load in the upper airways—by up to 100,000 times compared to those receiving the injectable vaccine. Furthermore, none of the healthy hamsters exposed to the nasal vaccine carriers became infected, whereas about half of those exposed to the injectable vaccine carriers did.
The study concludes that nasal vaccines could be pivotal in halting the spread of respiratory viruses. Boon emphasized that while the development of such vaccines has historically been challenging, future research may yield significant advancements in vaccines for respiratory infections.
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