WASHINGTON (AP) — Anticipating a green light from vaccine advisers, the Biden administration is assembling and shipping millions of COVID-19 shots for children ages 5-11, the White House said Monday. The first could go into kids’ arms by midweek.

“We are not waiting on the operations and logistics,” said coronavirus coordinator Jeff Zients.

By vaccinating children, the U.S. hopes to head off another coronavirus wave during the cold-weather months when people spend more time indoors and respiratory illnesses can spread more easily. Cases have been declining for weeks, but the virus has repeatedly shown its ability to stage a comeback, and more easily transmissible mutations are a persistent threat.

On Tuesday, a special advisory panel to the Centers for Disease Control and Prevention will meet to consider detailed recommendations for administering the Pfizer-BioNTech vaccine to younger children. The Food and Drug Administration already cleared the shots, which deliver about one-third of the vaccine given to adults. After CDC advisers make their recommendations, agency director Dr. Rochelle Walensky will give the final order.

Zients said the government has enough of the Pfizer vaccine for all 28 million children in the 5-11 age group. “We’re in great shape on supply,” Zients said during the White House coronavirus briefing.

The children’s vaccination drive is expected to start later this week and go into full swing by next week. Parents will be able to go to vaccines.gov and filter on vaccines for children 5-11 to find a location near them that is offering the shot.

Pfizer’s vaccine already has been authorized for use in older children.

After the FDA gave its authorization for younger children, the Biden administration asked states, territories and other jurisdictions to place their initial orders. Workers at the drug company and at distribution centers began the process of preparing and packing 15 million doses, said Zients.

“More doses will be packed and shipped and delivered,” he added. “More and more vaccine will come on line as we ramp up.”

The goal is for parents to have a range of options for getting children vaccinated, from pediatricians’ offices to clinics and pharmacies.

Walensky acknowledged both a sense of urgency and concern about getting children vaccinated. She stressed that clinical trials of the Pfizer vaccine for children have found it highly effective in preventing serious disease, with no severe adverse reactions in safety and efficacy trials.

“There has been a great deal of anticipation from parents,” Walensky said. “I encourage parents to ask questions.”

Separately, Zients announced that about 70% of U.S. adults are now fully vaccinated, while 80% have received at least one vaccine dose.