Pfizer-BioNTech COVID-19 vaccines for 12-to-15 year olds could be approved as early as next week by the U.S. Food and Drug Administration, expanding the U.S. immunization campaign to millions more people, NBC News reported Wednesday.

A clearance is highly anticipated after the pharmaceutical companies announced in March that the vaccine had been found to be effective, safe and generated strong antibody responses in adolescents in clinical tests.

Pfizer's COVID-19 vaccine has already been cleared for emergency use in the U.S. for people age 16 and above. The drugmaker declined to comment on the New York Times report, according to The Guardian.

"Many families are really ready for this," Dr. Kris Bryant, pediatric infectious disease specialist at Norton Children's Hospital, said.

The FDA authorization will be followed by a meeting of a federal vaccine consultative panel to discuss whether to recommend the shot for 12- to 15-year-olds.

News of the pending vaccine authorization comes as children now represent an increasing proportion of new COVID-19 cases in the U.S., where more than 100 million adults have so far been fully inoculated against the virus.

Rochelle Walensky, U.S. Centers for Disease Control and Prevention chief, said earlier last month that the vaccine could be granted approval by middle of May.

The clearance would be a major development in the U.S. immunization drive and welcome news to some families who are eager to protect their children before the start of the next school year.

"We're ready to move immediately to make about 20,000 pharmacy sites across the country ready to vaccinate those adolescents as soon as the FDA grants its OK," NBC quoted U.S. President Joe Biden as saying during remarks at the White House on Tuesday.

Meanwhile, Johnson & Johnson and Moderna are also testing their vaccines in 12- to 18-year olds, with data from Moderna's clinical trials expected to be released soon.