Mucous COVID-19 vaccines have the potential to save you from even mild infections and prevent transmission, a challenge that existing vaccines cannot address. But it’s too early to say that those vaccines, administered nasally, orally or transdermally, are the solution. that may stifle the pandemic, experts say.
He’s still a “beginner” for vaccines, said William Schaffner, MD, an infectious disease physician at Vanderbilt University in Nashville, Tennessee. Intranasal vaccines were expected to be to decrease transmission, but “this is more expected than demonstrated today,” he said.
He and mavens point to the lack of knowledge about the effectiveness of mucous COVID vaccines in humans and many demanding situations for the evaluation of progression and efficacy.
At least 12 nasal COVID vaccines are being developed, 4 of which have reached Phase III clinical trials.
The only approved intranasal vaccine of any kind in the United States is FluMist, a live attenuated flu vaccine. However, some countries have already approved mucous vaccines against COVID. Earlier this month, China approved an inhaled COVID-19 vaccine as a booster and India gave the soft green for an intranasal vaccine for emergency use, either in adenoviral vectors.
Achieve sterilizing immunity
Like peak respiratory viruses, SARS-CoV-2 enters the mucous membranes of the body, such as the mouth, nose, and throat. Once the virus has come into contact with mucous surfaces, it multiplies, traveling from those access points to the bloodstream to other parts of the body. picture.
The concept is that mucosal vaccines can boost immunity at those viral hotspots, preventing the pathogen from implanting, multiplying and transporting the body.
“We know that if you can induce immunity in the nose, it’s much more effective at preventing infections,” said Kathryn Edwards, MD, a professor of pediatrics and vaccine researcher also at Vanderbilt University. that we can start making weakened COVID vaccines that can stimulate local immunity and really save it from infection. “
There is growing evidence that higher levels of mucosal immunity do just that. For example, a research letter published in the New England Journal of Medicine showed that medical care tripled with higher levels of immunoglobulin A (IgA) in the mucous membranes had a reduced risk. of progression of infection with the Omicron variant (RR 0. 35; 97. 5% CI 0. 11 to 0. 91).
Current injectable vaccines, which help prevent progression to serious infection and death, induce some point of mucosal immunity, but at very low points, Mavens noted.
“Current vaccination methods are effective and adequate for preventing disease,” said Benjamin Goldman-Israelow, MD, PhD, assistant professor of internal medicine and infectious diseases at Yale School of Medicine in New Haven, Connecticut.
“We believe that additional immunization and immunity in the respiratory tract have the potential to further reduce transmission,” he said in an interview. Could this continue to inhibit viral evolution and the emergence of variants?All of those things, in our opinion, are very important. “
What are nasal vaccines like?
Animal studies comparing the effectiveness of mucosal vaccines against COVID-19 suggest that these vaccines would likely prevent infection further.
Goldman-Israelow and colleagues tested intranasal vaccines in mice, and apparently an unadjuvanted spike protein booster administered nasally and administered after an intramuscular injection of mRNA induced mucosal immunity, either reducing viral load in the respiratory tract and preventing fatal diseases.
In addition, Ahmed Hassan, PhD, and colleagues at the University of Washington in St. Louis found that a single-dose intranasal adenovirus vector vaccine reduced the threat of infection in rhesus respiratory tract macaques.
A promising combined technique in mouse studies led by Matthias Tenbusch, PhD, of the University Hospital of Erlangen, Germany. Intranasal recovery with adenoviral vectors induced high levels of IgA in the mucosa and pulmonary recall T cells, advanced the neutralization of the SARS-CoV-2 mucosa, and provided full coverage against infection in mice.
“Our knowledge suggests that mucosal booster immunizations after sensitization with mRNA are a promising technique for developing mucosal immunity in addition to systemic responses,” Tenbusch’s organization wrote.
Biotech company Codagenix has published phase I information on its attenuated intranasal vaccine, CoviLiv, which showed a strong immune and cellular reaction of the mucosa opposite to Omicron BA. 2.
However, there is still very little knowledge describing the effectiveness of intranasal vaccines in humans. Understanding how effective intranasal vaccines will be in preventing human infection and transmission will have to wait for the effects of Phase III clinical trials.
Obstacles to development
Despite promising assumptions, it may not be easy to assess clinical effectiveness, said John Moore, PhD, a professor of microbiology and immunology at Weill Cornell School of Medicine in New York.
Determining coverage correlates, that is, how much of the immune reaction will prevent infection, is a challenge in a population that has been largely exposed to the virus, he told MedPage Today.
“It’s a valid concept, but it will be hard to figure out that it’s bigger than we already have,” Moore said. Use only instead of just as reinforcement.
In addition, it is difficult to produce a durable and effective immune reaction with mucous formulas. FluMist, for example, was discontinued for an era following recommendations from CDC’s Advisory Committee on Immunization Practices (ACIP) after it was found to be less effective than flu vaccines injected into young people for several seasons. Now, the vaccine is for young people but not for adults over 49.
Gregory Poland, MD, a vaccine researcher at the Mayo Clinic in Rochester, Minnesota, added to the list of questions about those vaccines: What will durability and efficacy look like across all age groups?Will the antibodies generated neutralize all variants?
While intranasal COVID vaccines are a potentially attractive reaction for crowded environments, such as the military, college campuses or schools, Poland added: “Is this the answer for babies and the elderly, those who have the highest chance of being hospitalized or dying?Unmaximum probably without some kind of clinical breakthrough that hasn’t happened yet. “
Still, Poland said finding a vaccine that can block transmission could be only for the public health system at this point in the pandemic.
“I think it’s vital if we can do that,” he said, noting that at least another 100,000 people will most likely die from COVID each year at the speed of the virus’ spread. “So, yes, block the transmission? That would be a godsend. “
Amanda D’Ambrosio is a journalist on MedPage Today’s corporate and investigative team. He covers obstetrics and gynecology and new clinics, and writes articles about the U. S. physical health system. U. S. Follow