Health officials say the move adds 1.7 million people to the list of eligible New Yorkers for a total of nearly 16 million.
Teens aged 16 and 17 will be limited to receiving the Pfizer vaccine because it is the only one that has been authorized for use by people under 18.
Parental consent will also be required for vaccinations of 16-year-olds and 17-year-olds, with certain exceptions.
"Now is the time that we have to crush it, once and for all," Governor Andrew Cuomo said. "And the first step towards doing that is you have to take the vaccine, you have to take the vaccine."
Briana Justice admits she was worried to be among the first teens in the State of New York to be vaccinated for COVID-19.
"There was a lot of hype around the vaccine and so many people have an opinion on it," Justice said. "You don't know what's true, what's not true, who to trust. And I feel like, at the end of the day, as long as you have some sort of protection against the deadly virus, it's all worth it, in the end."
The State University of New York also announced plans to offer vaccines to tens of thousands of college students before they head home for the summer.
New York state health officials hope that increased eligibility will help cut down COVID-19 infections and hospitalizations - particularly among millennials and Generation Xers.
New York City will also allow seniors ages 75+ to walk-in to city-run vaccine clinics at 25 locations.
New York City schools say they will now get rid of the two case rule, which closed schools when two cases were found in a school.
This was causing the frequent closure of schools. While abandoning the previous mandate, Mayor Bill de Blasio has not said how many cases it will now take to close schools in the future.
And amid skepticism from the teachers' union about the mayor's new plan to ease criteria for COVID-19 school closings-Health Commissioner Dave Chokshi sounded upbeat.
"We do know that vaccination of school staff will help because the cases that we do see within the school setting are predominantly brought in by adults," Chokshi said. "So this gives us a very important layer of protection that we think can make our schools even safer."
The city also extended the opt-in period for in-person learning until this Friday.
On Monday, the state rolled out a new public service ad in hopes of convincing everyone, especially young people, to get vaccinated.
(The Associated Press contributed to this report.)
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