Because much of the world's population now has some type of immunity to SARS-CoV-2, whether from vaccination or infection, Iwasaki believes it's time to use nasal boosters instead of injected ones, in what she describes as the "prime and spike" strategy.
With so much invested in the mRNA platformmoney, time, and considerable public-health messaging to get people to trust these specific vaccinesit's a challenge to shift to a different type.
There are other questions of whether mucosal immunity against COVID-19 will be protective against disease, and whether that immunity will be enduring." That was also true of the other mRNA-based COVID-19 vaccines before they were approved, but regulators relied on measuring levels of neutralizing antibodies circulating in the blood, because those could be documented more easily than levels in tissues in the mucosa. It's impossible to answer such questions without testing nasal vaccines in people in clinical trials.
while injectable vaccines are effective in protecting people from getting sick with COVID-19, they are less able to block infection. In order to put the pandemic behind us, the world will need a way to stop infections and spread of the virus. That's where a different type of vaccine, one that works at the places where the virus gets into the body, will likely prove useful.
Here, though, the U.S. is losing its edge. In September, India approved a nasal COVID-19 vaccine, and in October, China began administering an inhalable onethe world's first such vaccine against any disease. Both countries conducted their own clinical safety and efficacy tests in humans (but have not yet published the complete and latest results).
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There may be some advantages to generating a more localized, IgA-heavy responseespecially at this point in the pandemic, when blocking people from getting infected with the virus in the first place has become more of a priority. Antibody-producing cells in tissues like the mucosa tend to produce IgA antibodies that clump viruses like SARS-CoV-2 together, making them easier to neutralize en masse. An international group of scientists also reported in December 2020 that IgA antibodies dominate the first wave of people's immune response in their saliva, blood, and lungs, in an effort to block the virus from infecting more cells. In a study published in June, researchers at the National Institute of Allergy and Infectious Diseases (NIAID) found that intranasal COVID-19 inoculation dramatically lowered the amount of virus detected in animals' respiratory tract. "We couldn't find virus in either the upper or lower respiratory tract, and we know the intranasal vaccine either prevented infection or eliminated infection within two days," says Bernard Moss, distinguished investigator at NIAID and senior author of the paper. Studies also show that people who have had COVID-19 tend to have high levels of IgA in the nose, and they are less likely to get infected if exposed to SARS-CoV-2 than people who haven't had COVID-19. That further suggests the importance of generating IgA antibodies to protect people from getting infected.
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Because much of the world's population now has some type of immunity to SARS-CoV-2, whether from vaccination or infection, Iwasaki believes it's time to use nasal boosters instead of injected ones, in what she describes as the "prime and spike" strategy. Her latest results support this strategy, as she and her team reported in Science that mice given an intranasal vaccine after receiving mRNA vaccination produced higher levels of IgA antibodies in the nose and mouth than either mRNA shots or a dose of the nasal vaccine alone. The prime and spike model also produced robust immune responses, involving more immune T cells, which are more durable than antibodies.
That belief is gaining ground among immune-system experts. "We are at a different stage in the pandemic," says Stephanie Langel, instructor in the department of surgery at Duke University who developed a nasal COVID-19 vaccine based on a modified cold virus and tested it in hamsters. "Boosting people with a nasal vaccine could help to reduce things like infection and transmission, which is going to be beneficial at a time when we are all going to be spending more time indoors in poorly ventilated spaces during the winter."
CanSino Biologics' vaccine was approved by Chinese health authorities as a booster dose for this reason. It's the same vaccine as the company's injected shotwhich is about 60% effective in protecting against COVID-19 symptoms one month or more after vaccinationbut in liquid-turned-mist form that is sprayed using a nebulizer in the mouth. Both vaccines use a disabled cold virus engineered to no longer be infectious, to deliver genes coding for the SARS-CoV-2 spike protein for the immune cells to recognize and target. While the results from late-stage human studies of the mucosal vaccine aren't available, the company published early-stage data that showed people receiving the inhaled dose generated similar levels of virus-fighting antibodies as people getting the injected form of the booster. An October release summarizing later stage trials said these levels of antibodies were higher among the people receiving the inhaled dose compared to the injected one.
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Indian health officials approved a nasal vaccine for primary vaccination in two doses given through the nose, but also have not yet published the results of the human studies supporting that decision. Its nasal vaccine also uses another modified virus to deliver SARS-CoV-2 spike genes. Iran and Russia also reportedly approved nasal vaccines developed by researchers in their respective countries, but without publicly available data.
Will nasal vaccines work?
Whether these vaccines will reduce infections won't be clear until more people have taken them. Real-world analysis of how well vaccinated people can fend off infections is likely going to be the most efficient way to measure whether nasal vaccines are working.
That's because there are no widely accepted ways to document the effects that a mucosal vaccine is having on the immune system. Scientists have much less experience with mucosal vaccines, and only a handful are approved, including one for influenza and the oral polio vaccine. That makes it difficult for health authorities to measure what the vaccines are doing and to know whether they're providing protection above and beyond existing vaccines. Most people make more IgA than any other major antibody, and these levels can vary among people, so it's hard to determine a standard level, which makes tracking changes nearly impossible.
"For intranasal vaccines, we don't have good biological correlates of immunity," says Hatchett, the CEO of CEPI. "There are other questions of whether mucosal immunity against COVID-19 will be protective against disease, and whether that immunity will be enduring." That was also true of the other mRNA-based COVID-19 vaccines before they were approved, but regulators relied on measuring levels of neutralizing antibodies circulating in the blood, because those could be documented more easily than levels in tissues in the mucosa. It's impossible to answer such questions without testing nasal vaccines in people in clinical trials.
That uncertainty has dissuaded biotech and pharmaceutical companies from investing in mucosal-based vaccines. While unprecedented financial support from the U.S. government fueled the development of mRNA vaccines, no such public sector resources are available for companies trying to develop a nasal vaccine. About a dozen companies have completed or are nearly finished with preliminary animal studies of various nasal vaccines, but they lack the funding needed to test their candidates in people through expensive clinical trials. "They have no financial support, no de-risking, nothing. They are in their own orbit," says Dr. Eric Topol, director of the Scripps Research Translational Institute; along with Iwasaki, Topol wrote an editorial in July supporting the need for broader vaccine research, including on nasal vaccines.
If successful, nasal vaccines could also help to improve vaccination rates in lower-resource countries where vaccination with the current vaccines, which require proper storage at ultra-low temperatures, has hampered immunization rates. Increasing vaccination with a shot that significantly decreases transmission is the only way to lower spread of the virus and ultimately contain it.
"This is going to be a decades-long engagement with this virus," says Hatchett. "Having easy-to-administer intranasal vaccines to reduce transmission will help us in terms of global access to vaccines. It's way too early to talk about eradication of COVID-19, but we're never going to eradicate COVID-19 if we can't prevent transmission."
https://time.com/6226356/nasal-vaccine-covid-19-us-update/?utm_source=twitter&utm_medium=social&utm_campaign=editorial&utm_term=health_covid-19&linkId=187942608&s=07