“My hope is that it’s going to be within the next month or so and not much later than that, but I can’t guarantee that,” Fauci said during a town hall event with Blue Star Families, a nonprofit group that supports military families.

Children under 5-years-old are currently the only age group not approved for vaccination against COVID-19 in the U.S. The FDA approved the Pfizer jab for children age 5 and older in October. Meanwhile, the FDA has only approved the use of COVID vaccines from Moderna and J&J for adults age 18 and up.

In December, Pfizer and BioNTech said they would submit test data on the efficacy of providing children under 5 with three doses of the COVID vaccine within the first half of the 2022 after tests revealed no safety concerns. The drug maker previously trialled two shots in children under 5 but extended the trial to include a booster shot. Pfizer said children’s immune systems responded less robustly than adults to only two doses of its Comirnaty COVID vaccine.

The approval could be lifesaving. According to the Center for Disease Control (CDC), the hospitalization rate for children under 5 reached its highest point in the pandemic this month, after Omicron became the dominant variant in the U.S. The CDC says a lack of vaccination is a likely reason for the increased hospitalization of children.

However, Fauci and the CDC have said that although the Omicron variant is more contagious, it doesn’t appear to cause greater illness than previous variants. The increased hospitalization rate, the CDC says, is likely due to Omicron spreading faster than other variants and infecting more people. But increased hospitalization will put extra strain on the U.S. health care system. Vaccinating children under 5 could ease that burden.