The 8-foot costumed character made the big announcement on Twitter Saturday -- the first time he's tweeted from his account since March. So, yeah ... major development for the reclusive BB.

Big writes, "I got the COVID-19 vaccine today! My wing is feeling a little sore, but it'll give my body an extra protective boost that keeps me and others healthy." He adds, "Ms. @EricaRHill  even said I’ve been getting vaccines since I was a little bird. I had no idea!"

No photo proof or anything showing Mr. Bird getting his jab, but we'll take him at his word here ... and even give him props for spreading the word on vaccine awareness.

Now, if you're wondering why he mentioned CNN's Erica Hill specifically -- it's because she and other CNN personalities hosted a "town hall" Saturday morning called "The ABCs of Vaccines," which featured a number of 'Sesame Street' puppets talking 'rona and the shot.

Of course, that includes Big Bird too -- and the reason they're all being recruited to even talk about vaccines at all is because the Pfizer jab was just approved for kids between 5 and 11 the other day ... and the government is encouraging parents to inoculate their children.

So, no Big Bird hasn't been holding out or "doing his own research" with vaccine hesitancy -- it's just that his core demographic is now eligible, and he wants to encourage them (and their parents) to get it done. Also, he's apparently only 6 years old or something? 🤷🏽‍♂️