The coronavirus may "spread more aggressively" in the winter, leading to a spike in cases in those months, former FDA commissioner Scott Gottlieb told CBS News' "Face the Nation" on Sunday.

What he's saying: "In the wintertime, you see respiratory pathogens spread more aggressively, in part because people are indoors more, they're in congregate settings," Gottlieb said.

• "[T]here is some impact of the cold weather on your ability to protect your upper airway from respiratory pathogens."
• Gottlieb said coronaviruses are typically not summer pathogens, but seasonal ones that "really manifest itself in the fall and winter."

Worth noting: Gottlieb said there's an "extremely low" likelihood a coronavirus vaccine is available for widespread use before the end of the year, following reports the CDC has requested governors "urgently" speed up permit applications so vaccine distribution sites are operational by early November.

• If a vaccine is available this year, Gottlieb said, it would likely be a "very staged introduction of the vaccine" for select groups that are at high risk for contracting the virus or for people who would be expected to have the worst outcomes from the disease.