Dr. Scott Gottlieb told CNBC on Monday that the highly transmissible variant of Delta-Covid, first discovered in India, could pose challenges for U.S. schools this fall amid lower vaccination rates in children.

“I think the reality is that more and more children are carriers of these new variants,” said the former Commissioner of the Food and Drug Administration in “Squawk Box”.

It’s only been a little over a month since the FDA approved Pfizer’s Covid vaccine for use in children ages 12-15. Moderna, also a two-shot regimen, asked the FDA to extend their emergency approval to teenagers aged 12-17. Pfizer’s EUA initially covered 16 years and older, while Moderna’s EUA is for 18 and older.

“The old assumptions about children and children [not] The community spread was based on the original strain of this virus, “he added.” With these new, more contagious varieties, I think we will see children and schools become more of a focus of the spread. “

There are studies testing Covid vaccines in younger populations. Pfizer and its German partner BioNTech expect data for children between the ages of 5 and 11 in the coming months.

Gottlieb pointed to coronavirus case data in the UK, where the Delta-Covid variant is more common than the US, and resulted in Prime Minister Boris Johnson delaying the reopening of the country. In the UK, the test-positive rate is significantly higher for people under the age of 24 than for people over 65, a cohort with more vaccine protection, Gottlieb said.

“There are some hopeful signs, but it’s an epidemic among schools, among younger unvaccinated people. Older people who are vaccinated aren’t the ones to spread this, and they don’t get that sick by and large,” Gottlieb said.

“The death rate has come down a lot, not necessarily because this is a less dangerous variant. We don’t think it is,” he added. “The death rate has dropped significantly because the people who would succumb to the virus are by and large vaccinated.”

Gottlieb said the accumulating evidence of the delta variant risk for unvaccinated people is unlikely to dramatically change the FDA’s approach to approving Covid vaccinations for children. That is already a priority and it will remain so, said Gottlieb, who headed the FDA in the Trump administration from 2017 to 2019.

However, he said the public health campaigns surrounding giving the vaccines to children, once they are eligible, could get more focus because of the Delta variant.

“I think above all I try [to get] vaccinated teenagers will be important as schools become more hotspots of spread and a more communicable burden that infects more children, even if it isn’t more dangerous, you will see more poor results, “Gottlieb said.

“It’s just mathematical that if more children become infected, even if the rate of bad outcomes in children is very low, more children will have bad outcomes because more of them will become infected,” he said.

Gottlieb added that he hopes schools will have some guidelines this fall to try to limit the spread of Covid. “Whether it’s masks or just distance and good prudent practices within the schoolhouse, I think smart schools will start the school year with some form of mitigation until they figure out where this goes.”

Reopening schools for personal tuition has been controversial throughout the pandemic. Citing multiple studies, the Centers for Disease Control and Prevention says on its website that when appropriate containment strategies are implemented, “transmission within schools is typically lower than, or at least similar, transmission in the community”.

Disclosure: Scott Gottlieb is a CNBC employee and a member of the board of directors of Pfizer, genetic testing startup Tempus, health technology company Aetion, and biotechnology company Illumina. He is also co-chair of the Healthy Sail Panel of Norwegian Cruise Line Holdings and Royal Caribbean.