Promising new research finds that people who are vaccinated against COVID-19 are less likely to spread the virus even if they become infected. Evidence suggests that COVID-19 vaccines render the virus less transmissible and infectious by enveloping the pathogen with antibodies.

According to NPR, Ross Kedl, a professor of immunology and biology at the University of Colorado Anschutz School of Medicine, says that the virus that vaccinated people shed is not as virulent as the virus that unvaccinated people transmit.

Kedl explains that the antibodies produced by vaccinated people coat the virus and make it less infectious. He points out that in cases “where you have these big breakthrough infections, there’s always unvaccinated people in the room.”

A recent study from Israel bears out Kedl’s theory. Researchers reported that in the case of breakthrough infections among healthcare workers “all 37 case patients for whom data were available regarding the source of infection, the suspected source was an unvaccinated person.”

Kedl tells NPR he has yet to see a report of a vaccinated person becoming infected “downstream—and could only be downstream—of another vaccinated person.”

Now there is new and surprising laboratory evidence that supports Kedl’s hypothesis. While mRNA vaccines, such as those manufactured by Moderna and Pfizer, were designed to circulate antibodies throughout the body, scientists have found evidence that they go beyond that purpose.

Michal Caspi Tal, a visiting scientist at Massachusetts Institute of Technology, and her colleagues found that in addition to circulating antibodies through the body, the vaccines deposited them in mucous membranes in the nose and mouth, which are primary entry points for COVID-19.

“This is the first example where we can show that a local mucosal response is made, even though the person got the vaccine in an intramuscular delivery,” noted Jennifer Gommerman, an immunologist at the University of Toronto who found similar results in her study.

The antibodies in the mucosal membranes cover the virus if it enters and renders it less infectious if the person coughs or sneezes, says NPR. Until the latest research, experts didn’t know that the vaccines could protect the upper airways and believed only a vaccine targeted into that area would be effective.

Not all scientists agree with the theory that antibodies in the nose and throat of vaccinated people coat the virus, but, according to NPR, there is mounting evidence that it becomes less dangerous thanks to vaccines. Whatever the mechanism, Kedl says that vaccination is a win-win situation.

“Because you’re going to get even more protected yourself,” he says. “And you’re going to be better off protecting people.”