SAN FRANCISCO — Twitter stated on Monday that it was suspending Representative Marjorie Taylor Greene from its service for 12 hours after she posted messages that violated its coverage in opposition to sharing deceptive details about the coronavirus.

Ms. Greene, Republican of Georgia, has been an outspoken opponent of vaccines and masks as instruments to curb the pandemic. In tweets on Sunday and Monday, she argued that Covid-19 was not harmful for individuals except they have been overweight or over age 65, and stated vaccines shouldn’t be required.

However circumstances of the coronavirus are on the rise, and the extremely contagious Delta variant accounts for greater than half of latest infections in america, federal well being officers stated this month. In Ms. Greene’s residence state, Georgia, new circumstances have elevated 193 percent previously two weeks.

Twitter stated Ms. Greene’s tweets have been misinformation, and it barred her from the service till Tuesday. “We took enforcement motion on the account @mtgreenee for violations of the Twitter Guidelines, particularly the Covid-19 deceptive info coverage,” a Twitter spokesman stated. The corporate additionally added labels to Ms. Greene’s posts in regards to the vaccines, calling them “deceptive” and pointing to details about the security of the inoculations.

In an announcement, Ms. Greene stated Silicon Valley corporations have been working with the White Home to assault free speech. “These Large Tech corporations are doing the bidding of the Biden regime to limit our voices and stop the unfold of any message that isn’t state-approved,” she stated.

Twitter took motion after President Biden referred to as on social media corporations to do extra to fight the unfold of vaccine misinformation on their platforms. On Friday, Mr. Biden stated that websites like Facebook were “killing people” by permitting misinformation to flourish unchallenged, including, “Look, the one pandemic we have now is among the many unvaccinated, and that — they usually’re killing individuals.”

His assertion capped weeks of frustration on the White Home over the unfold of on-line misinformation, which has led to vaccine hesitancy, well being officers say.

Fb, which took the brunt of the criticism, argued that Mr. Biden’s assertion was unfounded. “The Biden administration has chosen responsible a handful of American social media corporations,” Man Rosen, Fb’s vp for integrity, stated in a blog post on Saturday. “The actual fact is that vaccine acceptance amongst Fb customers within the U.S. has elevated.”

On Monday, the president softened his criticism, saying that exact customers have been accountable for the unfold of misinformation fairly than Fb. The corporate ought to do extra to fight “the outrageous misinformation” spreading on its platform fairly than taking his remarks as a private insult, Mr. Biden added.

Twitter has lengthy banned customers from sharing misinformation in regards to the coronavirus that might result in hurt. In March, the corporate introduced a policy that defined the penalties for sharing lies in regards to the virus and vaccines.

“We’ve noticed the emergence of persistent conspiracy theories, alarmist rhetoric unfounded in analysis or credible reporting, and a variety of unsubstantiated rumors, which left uncontextualized can forestall the general public from making knowledgeable choices relating to their well being, and places people, households and communities in danger,” the corporate stated in its policy in opposition to sharing Covid misinformation.

Individuals who violate that coverage are topic to escalating punishments referred to as strikes and will face a everlasting ban in the event that they repeatedly share misinformation in regards to the virus. A 12-hour ban, just like the one Ms. Greene is experiencing, is Twitter’s response to customers who’ve both two or three strikes. After 4 strikes, Twitter suspends customers for seven days, and after 5 strikes, Twitter bars the consumer altogether.

Different Republicans who’ve been suspended from Twitter have complained that the social media firm is censoring them.

In January, Twitter barred President Donald J. Trump after the corporate decided that his social media posts performed a job in inciting violence in the course of the riot on the U.S. Capitol. Mr. Trump has argued that Twitter and Fb, which also suspended his account, have been censoring him and stated the businesses required authorities oversight.

Ms. Greene was previously suspended from Twitter in April, however the firm stated it was a mistake attributable to one among its automated programs for detecting spam and abuse.

“Everybody is aware of that’s a LIE, and it was no mistake,” Ms. Greene tweeted after her suspension was lifted.