A switch in strategy is still early in development — no one should expect a whiff of vaccine this fall. Some scientists debate whether the goal of blocking transmission and mild infections is too lofty, and even proponents acknowledge the regulatory path could be complicated. The primary goal of vaccination is to protect people from severe sickness, not to prevent every mild case.

But the idea is gaining traction. Akiko Iwasaki, an immunologist at Yale University School of Medicine, said that in early 2021, she thought of her nasal vaccine research as preparation for the next pandemic. Then, the omicron variant changed the equation.

“Having seen all these new variants that are so much more transmissible and rendering our vaccines useless for infection prevention — that’s when we realized we may have the chance to contribute something during this pandemic,” Iwasaki said.