Worried about recent rise in COVID-19 cases? Here's how to protect yourself without getting a jab

In recent weeks, COVID-19 cases have been rising across Asia, with notable surges in Hong Kong, Singapore, and Thailand. In India, the Union Health Ministry reported 257 active cases as of Monday, May 19. Authorities remain on alert, particularly due to the global spread of the JN.1 variant, a sublineage of Omicron. While vaccines played a vital role in curbing the virus during the pandemic, researchers have now identified a promising alternative: a nasal vaccine. This new approach could prove to be safer, more effective, and better at blocking the virus at its primary entry point—the nose.

How are nasal vaccines different from traditional ones

A new study by Yale University researchers suggests that nasal vaccine boosters may provide safer and more targeted protection against respiratory illnesses like COVID-19—without relying on traditional immune-boosting additives. The findings were published in the journal Nature Immunology.

While most vaccines and boosters are delivered through injections into muscle tissue, typically in the upper arm, respiratory diseases such as COVID-19 may require protection at the virus's primary entry point: the respiratory tract.

“Our study shows how a simple viral protein antigen can boost respiratory tract immune responses against viruses,” said Akiko Iwasaki, Sterling Professor of Immunobiology at Yale School of Medicine (YSM) and senior author of the study. “These data imply that viral proteins in nasal spray may be used as a safe way to promote antiviral immunity at the site of viral entry.”

How do nasal vaccines work?

To explore how nasal vaccines work, researchers first gave mice a traditional mRNA COVID-19 vaccine via intramuscular injection. Later, they administered a booster dose through the nose. Their goal was to study the effectiveness of nasal boosters that don’t include adjuvants—special ingredients used in some vaccines to enhance and prolong immune responses. While adjuvants can boost immunity, they may also cause side effects such as inflammation and facial nerve swelling.

“We call this vaccine strategy ‘prime and spike’, which is where the mice were intramuscularly primed with mRNA vaccines followed by a nasal boosting with unadjuvanted spike protein,” Dong-il Kwon, a postdoctoral fellow in Yale’s Department of Immunobiology, said in a statement.

The scientists found that only the nasal booster triggered a strong local immune response. Other boosters, including intramuscular injection, didn’t produce much IgA or activate immune cells in the lungs of the mice. When the researchers gave the mice a second nasal booster, their IgA levels increased even more in both the lungs and nasal passages.

“These findings help explain why nasal boosters do not require adjuvants to induce robust mucosal immunity at the respiratory mucosa and can be used to design safe and effective vaccines against respiratory virus pathogens,” Kwon added.