Nearly 2,500 Big Apple adolescents received COVID-19 vaccines Thursday — the first day the shot was approved for 12- to 15-year-olds.

“There’s 6,000 appointments booked already,” Mayor Bill de Blasio said on WNYC radio Friday morning.

“We’re going to see a lot of young people vaccinated for sure. And we’re really excited about that,” he said.

The city has approximately 500,000 residents ages 12 to 15.

The youngsters got the Pfizer shot, which was approved by the CDC for the age group Wednesday.

Parents or guardians can find 250 immunization sites that offer the Pfizer shot via the Big Apple’s Vaccine Finder website.

Those locations include some of the city’s most familiar vaccination sites like the American Museum of Natural History, Citi Field and Staten Island’s Empire Outlets.

Although the city’s vaccine sites are open for walk-ins, people are encouraged to make an appointment by visiting https://vaccinefinder.nyc.gov/.