Nasal Spray Covid Vaccines: Hope or Hype?

A Closer Look at Biden’s $5 Billion “Project Next Gen”: Part I

On April 10, 2023, the White House announced the creation of a $5 billion project to in part create newer, better coronavirus vaccines. Focusing on nasal spray vaccines and universal coronavirus vaccines, the program was called “Project Next Gen.”

First, the good news. For healthy, young people, three doses of the mRNA vaccines made by Pfizer and Moderna likely offer a high level of protection against severe illness for years. These vaccines also offer a high level of protection against mild illness. But not for long. Several months after the last dose, protection against mild illness—which is characterized by a cough, runny nose, sore throat, fever, and muscle aches—fades. People with mild Covid aren’t hospitalized. Severe illness, on the other hand, requires hospitalization, usually for pneumonia.

Will nasal spray vaccines offer better protection against mild illness, virus shedding, and virus spread?

SARS-CoV-2 virus initially enters the body through the nose and throat. Wouldn’t it make sense, then, to induce an immune response where the virus enters, providing a first line of defense? “We're stopping the virus from spreading right at the border,” said Akiko Iwasaki, an immunologist at Yale University who studies nasal spray vaccines. “This is akin to putting a guard outside of the house in order to patrol for invaders compared to putting the guards in the hallway of the building in the hope that they capture the invader.”

Caution, however, should reign.

Nasal spray vaccines and vaccines given as a shot induce different kinds of antibodies. Vaccines given as shots induce immunoglobulin G (IgG), which hangs out in the bloodstream. Nasal spray vaccines, in addition to inducing IgG in the bloodstream, also induce immunoglobulin A (IgA), which resides on the lining of the nose and throat. Unfortunately, IgA, like IgG, is short-lived. A few months after an intranasal vaccine, virus-specific IgA will also begin to fade. 

Evidence for this limitation can be found in FluMist, a nasal spray influenza vaccine that has been available since 2003. FluMist has been far from a game-changer, failing to provide better or longer-lasting protection against mild infections than influenza vaccines given as shots.

Nasal spray Covid vaccines will likely offer some benefit in preventing mild infection and transmission above vaccines given as a shot—at least for several months. And children, virtually all of whom fear needles, would likely prefer them; as would adults who are needle phobic. Unfortunately, the hype surrounding nasal spray vaccines will likely exceed the hope.