Federal data indicates one-third of adolescents aged 12-15 are fully vaccinated against COVID-19 as the school year gets underway amid rising infections and a divide over mask mandates.

Dr. Francis Collins, director of the National Institutes of Health (NIH), noted the figure during an interview Monday, after he was pressed over the issue of yet-approved vaccine among younger children under 12 amid spread of the highly transmissible delta variant. Collins told CNBC co-hosts that use of the vaccine in kids younger than 12 is under careful review along with ongoing studies. Kids aged 12-15 are eligible for the Pfizer vaccine, however.

“They can get immunized right now,” Collins told CNBC co-hosts. “Sadly only about a third of them seem to have gotten those doses even as school is starting, that’s a lot of schoolrooms that could be protected if those parents would decide ‘yeah, let’s get our kids done.’”

Emerging reports have noted tens of thousands of students and staff across the country in quarantine due to COVID-19 exposure or infection just weeks into the school year, including at least 23,000 staffers and students at metro Atlanta schools, some 8,400 students and 307 district employees in the Tampa area, and upwards of 1,000 students and staff in Fort Worth, Texas.

As of Aug. 22, the Centers for Disease Control and Prevention (CDC) reported 33.9% of kids aged 12-15 are fully vaccinated, and 46.9% have received at least one dose. Meanwhile, as COVID-19 cases surge around the country, a majority of Americans say they support mask mandates for students and teachers in K-12 schools, according to a new poll, but their views are sharply divided along political lines.

About 6 in 10 Americans say students and teachers should be required to wear face masks while in school, according to a poll from The Associated Press-NORC Center for Public Affairs Research. Similar shares say teachers and eligible students should also be required to receive a COVID-19 vaccine. Masks have been a point of contention as U.S. schools reopen amid rising numbers of coronavirus cases. Questions about whether to require them have caused turmoil among parents and politicians, with some Republican governors banning mask mandates even as President Biden threatens legal action against them. In a reflection of that polarizing debate, the poll finds a wide partisan divide. About 3 in 10 Republicans said they favor mask requirements for students and teachers, compared with about 8 in 10 Democrats. There was a similar split over vaccine mandates in schools.

The CDC has recommended universal indoor mask-wearing for teachers, staff and students regardless of vaccination status this fall, among other mitigation measures, citing the rapid spread of the delta variant.

In some areas with school mask mandates, tensions have flared in recent weeks. Protesters opposing mask requirements have filled school board meetings from Maryland to California, in some cases disrupting meetings and forcing them to postpone.

In the meantime, federal officials at the Food and Drug Administration hope that the new full approval of Pfizer’s COVID-19 vaccine in individuals ages 16 and older will boost confidence in those hesitant to receive the shot under emergency approval. CDC data indicate that 44% of teens aged 16-17 are fully vaccinated against COVID-19, with 55.8% receiving at least one dose.

“We know that for some people, FDA approval of a COVID-19 vaccine may give them the confidence to get vaccinated,” Dr. Peter Marks, director of the FDA Center for Biologics Evaluation and Research, told reporters over a call Monday. “By following our rigorous processes to evaluate this application, we hope those who have waited until now to make the choice to protect themselves and thereby also protect their communities by reducing the spread of COVID-19 will go and get vaccinated.”

Parents of adolescents and teens eligible for shots have additional concerns, like the vaccines’ rapid development and risk of rare adverse event post-vaccination called myocarditis, according to a report. Shortly after the FDA announced Pfizer’s full approval Monday, Marks noted that safety data demonstrated an increased risk of myocarditis, or heart inflammation, among males under 40, with males aged 12-17 facing the highest observed risk. However, available data suggest most patients’ symptoms have resolved.

The Associated Press contributed to this report.