The company stopped taking action against tweets that were in breach of its Covid rules on Wednesday 23 November, according to its website.
The social media platform had previously reported suspending more than 11,000 accounts for Covid misinformation as of September 2022.
It also removed almost 98,000 pieces of content which breached those rules, according to statistics published by Twitter. The new change was not formally announced, but some Twitter users spotted a note on the page outlining its policy.
It said: "Effective November 23, 2022, Twitter is no longer enforcing the COVID-19 misleading information policy."
The update appeared below a line that still reads: "As the global community faces the COVID-19 pandemic together, Twitter is helping people find reliable information, connect with others, and follow what’s happening in real-time."
Other policies on false information remain on Twitter, without a similar notice saying they will not be enforced.
Under its Covid-specific policy, Twitter used a "five-strike system" for accounts posting "demonstrably false or misleading" content which may "lead to a significant risk of harm", such as exposure to Covid or damage to public health systems.
No action would be taken against accounts tweeting disinformation once. Users with two or three strikes could be locked out of their accounts for 12 hours. Those with four strikes would be locked out for seven days, but repeat offenders could be suspended for a matter of hours, days - or even indefinitely if they received five strikes against their account.
Elon Musk’s amnesty plan
Twitter owner Musk has also announced a "general amnesty" for suspended Twitter accounts, "provided that they have not broken the law" or engaged in "egregious spam." This means that some of those who breached the rules are now able to return to the platform.
Several accounts, such as that of former US President Donald Trump, have already been reinstated by Mr Musk since his takeover.
The billionaire made the announcement on Twitter on 20 November after asking users to click “yes” or “no” on whether Mr Trump’s account should be restored.
Twitter users narrowly backed the move with 51.8% of more than 15 million voters choosing “yes”. “The people have spoken. Trump will be reinstated. Vox Populi, Vox Dei,” Musk tweeted after the vote, using a Latin phrase meaning “the voice of the people, the voice of God”.
The move reverses a ban that kept the former US president off the social media site since a pro-Trump mob stormed the US Capitol in Washington on 6 January 2021 as Congress was poised to certify Joe Biden’s election victory. His account was suspended due to the risk of incitement of violence.
Despite the reinstatement, it is not yet clear whether Mr Trump will actually make a return to Twitter after earlier saying: “I don’t see any reason for it”. He was an irrepressible tweeter before he was banned, but the former president has said in the past that he would not rejoin the social media platform even if his account was reinstated.