CDC Director Dr. Robert Redfield said that the possibility of a flu pandemic is something that keeps him from getting rest at night.
Redfield made the remarks during an interview with "CBS This Morning," which aired on Tuesday.
What are the details?
Redfield told "CBS This Morning" co-host John Dickerson that one of his greatest fears for modern society is a flu pandemic.
The Spanish Flu killed about 50 million people 100 years ago, and Redfield explained that it's "very possible" for something of that magnitude to happen again.
"You know, people ask me what keeps me up at night," Redfield said. "And the thing that keeps me up at night is just what you brought up: pandemic flu. So I think it's very possible.
"We're at risk for another pandemic,: he added. "Our best preparation for that pandemic is to optimize our response to seasonal flu."
Redfield went on to reiterate that a flu pandemic is "remains a serious possibility."
An estimated 80,000 Americans died from the flu and its complications during the 2017 flu season, which the government says is the flu's highest death toll in about 40 years.
"We lost more children last year from flu deaths than any year before since we started recording," Redfield admitted. "The majority of those children that died were not vaccinated."
Redfield went on to stress the importance of flu vaccinations for all.
"I want to come back and argue that immunization is one of the most critical tools we have to eliminate diseases," he said. "In this case, it's the most important tool we have to minimize flu."
Redfield noted that the most "powerful tool" in the CDC's arsenal against disease eradication or reduction is vaccination.
"We're on the verge of eliminating polio from the world," Redfield explained. "There's 22 cases of polio right now. How did we get on the verge? Vaccination."
The Centers for Disease Control recommends that all people age 6 months and older receive an annual flu vaccination, and also recommends that people get a flu vaccine each year by the end of October.
In September, the CDC reported that a 2014 study "showed that flu vaccine reduced children's risk of flu related pediatric intensive care unit ... admission by 74 percent" in recent flu seasons.
Also, the vaccine has reportedly reduced "the risk of flu associated-hospitalizations among adults on average by about 40 percent."
You can read more about the flu and the importance of vaccines here.