The U.S. is heading toward a pandemic “double whammy” this winter, according to Dr. Anthony Fauci, but it could still be avoided if enough people get a third vaccine shot. In an interview aired at the 2021 STAT Summit on Tuesday, the White House chief medical adviser warned that the combination of waning immunity among the vaccinated and the highly transmissible delta variant could cause trouble this winter. Fauci said: “The somewhat unnerving aspect of it is that if you keep the level of dynamics of the virus in the community at a high level—obviously the people who are most vulnerable are the unvaccinated—but when you have a virus as transmissible as delta, in the context of waning immunity, that dynamic is going to negatively impact even the vaccinated people.” Fauci went on to say that he believes that booster doses of the COVID vaccine may become the standard for a “full” vaccination, adding: “A booster isn’t a luxury; a booster isn’t an add on.”