Sep 13, 2022 - Health

Why we need to be talking about vaccines that offer "mucosal immunity"

Illustration of squiggly arrows pointing at a nose.
Illustration: Shoshana Gordon/Axios

As the U.S. rolls out updated mRNA-based COVID shots, a growing chorus of experts say it's a mistake not to focus on treatments that boost immunity through mucous membranes.

Why it matters: Next-generation nasal or oral vaccines could quickly boost the immune response in the very airways where COVID-19 enters the body and ultimately break our reliance on the constant development of reformulated shots to target new variants of concern.

  • But the U.S. isn't putting money into such products, which experts say could augment current vaccines on the market.

Driving the news: China made headlines this month for the emergency approval of CanSino's inhaled COVID-19 vaccine. Last week, India approved Bharat Biotech's intranasal vaccine for emergency use.

  • Both claim to stimulate mucosal immunity, which not only protects against the virus, but blocks it from spreading.
  • They come on the heels of research in Science Immunology this summer saying mucosal booster vaccination is needed to establish robust "sterilizing immunity" against COVID, including infection by Omicron variants and future variants of concern.

State of play: Experts say mRNA shots did a remarkable job protecting against infection and the spread of earlier strains of COVID. They also continue to keep people from being hospitalized or dying.

  • But they don't prevent transmission in a way that could actually end the pandemic.
  • Eric Topol, executive vice president of Scripps Research, points to the number of reinfections as the more contagious Omicron variant swept the nation.
  • "That signified that we had a leak. A big leak. That leak is the fact Omicron has become so much more transmissible, so much more able to get into our upper airway," Topol said.
  • The answer he, and other experts say, could lie in vaccines that work in the membranes where respiratory diseases take root.

Be smart: Mucosal membranes are the moist, inner lining of some organs and body cavities, such as the nose, mouth, lungs, and stomach.

  • Mucosal immunity is a key compartment in our immune system, different from the antibody response in the blood that's stimulated by vaccine shots, said Michael Mina, an epidemiologist and chief scientific officer for at-home testing company eMed.
  • "Muscosal immunity has evolved to recognize what you need immunity to and where — so it's much more localized," he said. "You could spray a nasal vaccine into a somebody's nose and that's where a lot of those immune cells will actually populate."
  • There are other oral and spray vaccines on the market, such as AstraZeneca's FluMist Quadrivalent flu vaccine.

Between the lines: Experts have expressed ongoing frustration with the lack of enthusiasm for bulking up our arsenal with new weapons against COVID.

  • A number of smaller biotechs in the U.S. have been working on next-generation vaccine candidates. For example, Vaxart, which recently reported promising Phase 2 trial results, says its oral vaccine tablet stimulated a mucosal response.
  • And researchers from the Catholic University of America and the University of Texas Medical Branch in Galveston demonstrated an effective intranasal COVID vaccine tested in mice in July.
  • Late last month, Senate Republicans sent a letter to the Biden administration calling for an Operation Warp Speed-like project for intranasal vaccines to reduce transmission, as well as pan-coronavirus approaches.
  • "We continue to do our part, including by hosting a vaccine summit in July to talk about next-generation COVID needs including a mucosal vaccine, but we need Congress to provide funding to innovate and continue fighting this pandemic with the best tools possible," a White House spokesperson said in a statement.

What they're saying: "It just hasn't been a priority in this country," Topol said.

  • "If we don't put up a wall, a mucosal wall of immunity, we're succumbing to the viruses' enhanced ability to spread and induce infection," he said. "We're surrendering."
  • There are a number of vaccine technologies, including those that stimulate a mucosal response, that have been choked out of the COVID response, Mina said.
  • "We got really comfortable with one platform, the mRNA. And I think we did that at the expense of really putting the same level of resources into whole different classes of vaccines," Mina said.
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