Delayed vaccine shipment leaves New York City with 'extra' supply, city to open overnight appointments

"We're going to blitz this week," the mayor said.

De Blasio said the city is adding overnight shifts at three mass vaccination sites: Brooklyn Army Terminal, Bathgate in the Bronx and Citi Field in Queens.

"We're going to blitz this week. This is going to be a very intense weekend," de Blasio said at a news conference Thursday.

De Blasio said the city is also "doubling the number of appointments at some of the key sites in communities where we're focusing on fighting disparity, at Teachers Prep and at Martin Van Buren high schools. We're opening new pop-up sites in communities that need more outreach."

"We get the supply we need, we can take off," he said.

New York City had administered more than 1.6 million vaccine doses -- which equals more than the entire population of Philadelphia, the mayor said.

New York City's seven-day positivity rate stands at 7.12% as of Thursday.

ABC News' Ahmad Hemingway contributed to this report.