A preliminary study has shown that in the case of a breakthrough infection, the Delta variant is able to grow in the noses of vaccinated people to the same degree as if they were not vaccinated at all. The virus that grows is just as infectious as that in unvaccinated people, meaning vaccinated people can transmit the virus and infect others.

Previous studies in hospitals in India; Provincetown, Massachusetts; and Finland have also shown that after vaccine breakthrough infections with Delta, there can be high levels of virus in people’s nose whether they are vaccinated or not. The next logical step was to determine whether vaccinated people could shed infectious virus. Many experts