Dr. William Schaffner, a professor at Vanderbilt University Medical Center, echoed Walensky’s take on how vaccination lowers the intensity of Covid-19 symptoms when breakthrough cases happen.

“This is largely a problem when it comes to severe disease, the disease that requires hospitalization, it’s among the unvaccinated. It really is pretty unusual to have a vaccinated person be hospitalized. Most of those people tend to be older and very, very frail. They never were able to respond to the vaccine, and we have the occasional immunocompromised person whose immune system also couldn’t respond optimally to the vaccine,” Schaffner told CNN on Thursday.

“So the unvaccinated continue to be the big highway of transmission. The vaccinated, they’re little side streets. Let’s not get preoccupied with that. We need to get more people vaccinated.”

And if more people do in fact get their shots, case surges can be controlled in a matter of weeks, Walensky said Thursday.

“However, our models show that if we don’t (vaccinate people), we could be up to several hundred thousand cases a day, similar to our surge in early January,” she said.