Nasal COVID Vaccine Stops Infection in Animal Trials

• August 1, 2024
• Dennis Thompson HealthDay Reporter

A next-generation nasal vaccine for COVID-19 appears to do what injectable vaccines can’t -- actually stop the spread of the virus from person to person.

Hamsters that received the nasal vaccine didn’t pass the virus on to others if they became infected, breaking the cycle of transmission, researchers reported July 31 in the journal Science Advances.

The animal study provides more evidence that vaccines delivered into the nose or mouth might be the key to controlling the spread of respiratory infections like influenza and COVID, researchers said.

“To prevent transmission, you need to keep the amount of virus in the upper airways low,” said senior researcher Jacco Boon, a professor of medicine, molecular microbiology and pathology & immunology with the Washington University School of Medicine in St. Louis.

“The less virus that is there to begin with, the less likely you are to infect someone else if you cough or sneeze or even just breathe on them,” Boon added in a university news release. “This study shows that mucosal vaccines are superior to injected vaccines in terms of limiting viral replication in the upper airways and preventing spread to the next individual.”

“In an epidemic or pandemic situation, this is the kind of vaccine you’re going to want,” Boon concluded.

Although the first COVID vaccines succeeded in reducing serious illness and death, the shots could not prevent the spread of the virus. A mildly ill vaccinated person could still pass the virus to someone else.

Viruses like the flu, COVID and RSV multiply rapidly in the nose, allowing them to spread from person to person through coughs, sneezes and even breathing, researchers said.

Traditional injectable vaccines are much less potent in the nose than in the bloodstream, which leaves the nose relatively unprotected against viruses that multiply quickly and spread easily.

Researchers have long theorized that a vaccine administered to the nose or mouth through spray or droplets could reduce disease transmission by triggering an immune response right where it’s needed most.

For this study, researchers used a two-step process to test a nasal COVID vaccine used in India against the injectable Pfizer vaccine in a group of hamsters.

Hamsters are naturally susceptible to COVID, unlike mice, making them a better lab animal with which to study virus transmission, the researchers explained.

After giving the vaccinated hamsters a few weeks to develop a full immune response, researchers infected other hamsters with COVID and put them all together for eight hours.

Most of the vaccinated hamsters became infected, with coronavirus found afterward in the noses of 12 of 14 who got the nasal vaccine and 15 of 16 who got the jab, researchers said.

However, the hamsters that got the nasal vaccine had virus levels in their airways that were 100 to 100,000 times lower than that of hamsters vaccinated with a shot, results show.

In the second step, researchers took vaccinated hamsters that became infected and placed them with other healthy hamsters for eight hours.

None of the hamsters exposed to nasally vaccinated hamsters became infected, regardless of whether the new hamsters had been vaccinated or not, results show.

On the other hand, about half of the new hamsters exposed to those vaccinated by injection became infected, researchers said.

Vaccination through the nose broke the cycle of transmission, researchers concluded.

“Mucosal vaccines are the future of vaccines for respiratory infections,” Boon said. “Historically, developing such vaccines has been challenging. There’s still so much we don’t know about the kind of immune response we need and how to elicit it. I think we’re going to see a lot of very exciting research in the next few years that could lead to big improvements in vaccines for respiratory infections.”

More information

The U.S. Centers for Disease Control and Prevention has more about COVID vaccines.

SOURCE: Washington University School of Medicine, St. Louis, news release, July 31, 2024

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