Actress Letitia Wright has become embroiled in controversy after sharing a video making unsubstantiated claims about the safety of Covid-19 vaccines.
The Black Panther star posted a link to a video whose host said people taking the vaccines would have to "hope it doesn't make extra limbs grow".
After being criticised on Twitter, she said she wasn't against vaccines but it was important to "ask questions".
The BBC has contacted Wright's representatives for comment.
In the video, presenter Tomi Arayomi explains he is a "big sceptic of needles and vaccinations in general" and hasn't decided whether to take a Covid vaccine.
While discussing his doubts about their safety and effectiveness, he also admits "I don't understand vaccines medically", and doesn't present medical evidence.
Wright's initial post, which has been retweeted more than 3,000 times, featured a link to the video along with the prayer hands emoji.
She then became involved in heated exchanges with users who accused her of spreading misinformation.
"It is not my intention to make anyone upset, nor am I saying don't take it," she wrote. "I'm just concerned about what's in it that's all. Isn't that fair to question?"
The UK's medicines regulator has approved the first vaccine, made by Pfizer and BioNTech, saying the process had been robust with safety considerations paramount. Regulators around the world are assessing the safety of that and other vaccines.
Wright stood by her comments after the backlash, adding: "If you don't conform to popular opinions, but ask questions and think for yourself... you get cancelled."
my intention was not to hurt anyone, my ONLY intention of posting the video was it raised my concerns with what the vaccine contains and what we are putting in our bodies.— Letitia Wright (@letitiawright) December 4, 2020
Her co-star in the Marvel Cinematic Universe, Don Cheadle, also became involved after Twitter users copied him in to her tweets.
The actor said he had watched some of the video and described its content as "hot garbage", adding that he would raise the issue with Wright directly.
Arayomi's video remains on YouTube. The company recently pledged to delete misleading claims about coronavirus vaccines.
Last month, Labour called for financial and criminal penalties for social media firms that do not remove false scare stories about vaccines.
The BBC's disinformation reporter Marianna Spring explained: "Baseless conspiracy theories about a coronavirus vaccine have been spreading on social media for months - and the latest vaccine news rekindled these pre-existing narratives online.
"Within hours of news breaking about the Pfizer/BioNTech vaccine, comments and memes suggesting it will deliberately harm us were popping up in local Facebook groups, parent chats and on Instagram.
"This kind of disinformation is worlds away from legitimate concerns that a vaccine is safe and properly tested."
Wright was recently seen in one of Oscar-winning director Steve McQueen's Small Axe films on BBC One.
Wright has previously starred in the Avengers films Infinity War and Endgame, and won the rising star prize at the Bafta Film Awards last year.