3:35 PM PT -- Powell explained his decision to transfer to TMZ Sports ... saying he believes the vaccine should not be mandatory because "people are getting the shot and still getting sick."
Powell tells us he contracted COVID before last season -- and said he had "a headache for a few days but I'm fine and feel like I don't need the vaccine."
The DB says he's getting a lot of criticism for his decision -- but added he believes it's unfair.
"It's not like I'm telling anybody else what to do or how to feel about anything," Powell said. "I don't understand why people are acting like I did something that impacts them personally."
Powell tells us schools have reached out to him since his decision to transfer.
Rutgers football player Peyton Powell says he's transferring ... claiming it's all 'cause the university has made it mandatory for students to get the COVID vaccine.
The school announced back in March if students wanted to attend classes and play football for the university, they'd have to get the shots.
"We are committed to health and safety for all members of our community," Rutgers president Jonathan Holloway said when announcing the decision.
"Adding COVID-19 vaccination to our student immunization requirements will help provide a safer and more robust college experience for our students."
Powell says after considering the school's choice ... he's now decided to leave the university in search of one that will not make the vaccine mandatory.
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"The University of Rutgers has made the COVID vaccine mandatory to attend school and play football," Powell said Tuesday on his social media page.
"Therefore I have no other choice but to enter my name into the transfer portal."
The move will mark the second time in Powell's college football career that he's transferred ... the 6-foot-2, 185-pound DB was at Baylor during his freshman season in 2019 before switching to the Scarlet Knights.
Before that, Powell was a touted 4-star recruit from Permian High School in Texas.