Former Food and Drug Administration Commissioner Dr. Mark McClellan told CNBC that it seems realistic that younger kids will be getting vaccinated for Covid-19 based on the new data released by Pfizer on Monday. McClellan explained the FDA's rigorous review process during a Monday evening interview on "The News with Shepard Smith." When it comes to the overall fight to combat Covid, McClellan told host Shepard Smith that if children can start getting vaccinated, "it will make a big difference in keeping schools safer in preventing the kinds of spread that we're seeing now."