A new study has shown promising results for a nasal COVID-19 vaccine, according to researchers at the Institute of Virology at Freie Universität Berlin in Germany. 

When two doses of the live nasal vaccine were administered to hamsters, the animals showed a stronger immune response compared to their response to two doses of the vaccines that are currently available.

The study was published in the journal Nature Microbiology on Monday.

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The lead author of the study told Fox News Digital this week, "We find that a live attenuated vaccine prevents virus replication — this could be a game changer in controlling SARS-CoV-2 transmission."

Today, there are four approved COVID vaccines in the U.S. — all of which are administered via injection into the muscle, per the Centers for Disease Control and Prevention (CDC).

The Pfizer-BioNTech and Moderna vaccines are both mRNA vaccines, which use mRNA (messenger RNA) to trigger cells to produce a viral protein. 

This prompts the immune system to create antibodies.

Johnson & Johnson’s Janssen is a viral vector vaccine, which delivers DNA "instructions" to the body’s cells via a different, non-harmful virus.

The Novavax vaccine is a protein subunit vaccine, which uses some proteins of the virus that causes COVID-19 — known as the "spike protein" — to "train" the immune system to act against future spike proteins.

The nasal COVID vaccine that's being tested is a live-attenuated vaccine, which means it contains a live but weaker form of the coronavirus. 

It works by stopping the virus in the upper airway before it can travel further into the body.

The researchers used Syrian hamsters for their vaccine testing. 

The study’s lead author, Dr. Jakob Trimpert, head of diagnostics at the Institute of Virology at Freie Universität Berlin in Germany, said hamsters are the "prime non-transgenic [not genetically modified] small animal model" for COVID-19 research.

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"These animals have the great advantage of being naturally susceptible to SARS-CoV-2 infection, including natural spread between hamsters," he explained to Fox News Digital. 

"The infection of Syrian hamsters resembles many key features of moderate human COVID-19 — this makes the hamster an ideal model to study COVID-19 vaccines and therapies."

The nasal vaccines have significant advantages over the injectable vaccines that are currently available, Dr. Trimpert said. 

"An intra-nasally applied live-attenuated vaccine provides superior protection against SARS-CoV-2 infection compared to intramuscularly applied vaccines," he told Fox News Digital.

While he said currently marketed vaccines do a good job of preventing severe illness from COVID, Dr. Trimpert pointed out that they don't prevent the infection, moderate illness or spread.

"We find that a live attenuated vaccine prevents virus replication" — so "this could be a game changer in controlling SARS-CoV-2 transmission."

The main benefit of a nasal vaccine is that immunity is activated right where it’s needed, Dr. Trimpert said.

"It is the induction of local immunity at the site of natural infection that could be a game-changer here," he said. 

"Judging from our results, this has considerable impact and greatly reduces the risk of infection."

Dr. Marc Siegel, professor of medicine at NYU Langone Medical Center and a Fox News medical contributor, said he finds this new research promising. He was not involved in the study.

"The goal is very important: to create a barrier to stop virus spread," he told Fox News Digital.

"This involves IGA antibodies and works at the level of the mucus membranes." 

IGA, or Immunoglobulin A, is an antibody that plays an important part in the immune function of mucous membranes.

The mucous membrane, or the nasal mucosa, is the tissue that lines the nasal cavity.

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The nasal vaccine could be standalone or could work in conjunction with other vaccines, said Dr. Siegel. 

"If it’s effective and human trials of the German vaccine are ongoing, it will be a big step forward," he said.

Dr. Norman B. Gaylis, who has treated over 1,000 patients at his Long Haul COVID Clinic in Aventura, Florida, also reviewed the findings.

"I believe it’s a brilliant idea to create a vaccine that can build immunity in the nasal mucosa," he told Fox News Digital. 

"Research has shown that COVID and other viruses often enter through the nose, and travel up the olfactory nerve … and then into the brain," he explained.

Developing a nasal vaccine could help prevent viruses from gaining easy access to the brain, said Dr. Gaylis. 

"This is important because many ‘long COVID’ patients are reporting brain damage from the virus," he added.

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Additionally, a nasal vaccine would provide a helpful alternative for patients who have a fear of needles, allowing them to get protected without a jab, said the doctor.

As of July 2022, there were at least 12 nasal COVID vaccines in clinical development, according to Science Immunology.

The biotechnology company Codagenix announced in October 2022 that it had entered the Phase 3 clinical trial for CoviLiv, its intranasal COVID-19 vaccine that is intended for healthy adults.

The Icahn School of Medicine at Mount Sinai in New York City has launched a Phase 1 study evaluating a new egg-based COVID vaccine, called NDV-HXP-S, which can be administered nasally or via muscular injection.

In June 2022, the National Institute of Allergy and Infectious Diseases published a study illustrating the effectiveness of nasal COVID vaccines in hamsters. 

This was followed by another study in September 2022, which showed that nasal vaccines produced a strong immune response in rhesus monkeys.

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Both China and India have approved nasal COVID vaccines for humans, as reported in the journal Nature in September 2022.

Iran and Russia have also approved nasal forms of the vaccine, though there is limited data available about their effectiveness.

The German research team plans to continue investigating the effectiveness of its vaccines and looks forward to moving into clinical trials.

"While our results in the animal model are robust, only clinical trials will be able to ascertain translatability to human medicine," Dr. Trimpert said.

Questions remain about the vaccine’s safety for people with weakened immune systems and the potential risk of combining it with different variants of the virus.

The CDC states that severely immunocompromised people and pregnant women should avoid live vaccines.

Said Dr. Trimpert, "We do think there is reason to hope for next-generation COVID-19 vaccines that better control virus transmission and greatly reduce disease burden."