Social media platforms are failing to monitor anti-Semitism, two reports say.

“While it has been a significant accelerator over the past year and a half, the global pandemic isn’t the origin of many of the conspiracy theories about Bill Gates currently circulating across media,” said Jennifer Granston, head of insights at Zignal Labs. “Rather, it is the gasoline being poured on a fire that’s been smoldering for more than a decade.”

According to research from the media insights company Zignal Labs, which tracked narratives about Mr. Gates on social media and cable television and in print and online news outlets from June 2020 to June 2021, as many as 100,000 mentions were made in the last year about Mr. Gates’s connections to the Chinese government.

In one example, an article on The National Pulse, a far-right website, suggested without evidence that Mr. Gates, a co-founder of Microsoft, could have influenced the U.S. relationship with China because a relative had once worked in a government job loosely related to U.S.-China relations when President Biden was vice president. Another article in The National Pulse listed several instances in which Microsoft worked with Chinese companies, and people online pointed to this as evidence Mr. Gates must be conspiring with the Chinese government. Both articles potentially reached hundreds of thousands of followers on Facebook according to data from CrowdTangle, a Facebook-owned social media analytics tool.

Mr. Gates was mentioned another 260,000 times in falsehoods about climate change, according to Zignal. One unfounded claim is that Mr. Gates was funding a plan to dim the sun. (In reality, he is financially backing a small-scale experiment from Harvard University that aims to look at whether there are aerosols that could reduce or eliminate the loss of the ozone layer.) In another, conspiracy theorists say that Mr. Gates is pushing a plan to force people in rich countries to eat only “100 percent synthetic beef” because he had a financial stake in a company making those products. (Mr. Gates did say it was a good idea for developed nations to consider the idea, but it was part of a larger conversation about tech breakthroughs and energy policies to tackle the effects of climate change.)

Those falsehoods, while popular, still pale in comparison to those about his profiteering off the coronavirus. In one popular unfounded claim, Mr. Gates is accused of wanting to surveil the population with microchip vaccination implants (159,000 mentions). Mr. Gates’s philanthropy work in distributing vaccines to developing countries had also been twisted into unfounded accusations that he was trying to cull the global population (39,400 mentions). And a third popular falsehood pushed by conspiracy theorists is the notion that Mr. Gates advocated vaccine passports in order to further a tech-enabled surveillance state (28,700 mentions).

According to Zignal Labs, the sharing of tweets linking Mr. Gates to the vaccine passport narrative actually spiked during the time of Mr. Gates’s divorce announcement from his wife of 27 years, Melinda French Gates, with whom he ran the Bill and Melinda Gates Foundation. The breakup has set off new scrutiny of his conduct in work-related settings.

“Bill Gates: privacy please everyone,” said one tweet, which was liked and shared more than 30,400 times. “Also Bill Gates: we need vaccine passports.”

“Strangely, some people who participated in the riot haven’t been charged,” Mr. Carlson said. “Look at the documents. The government calls these people ‘unindicted co-conspirators.’ What does that mean? It means that in potentially every case, they’re F.B.I. operatives.”

The Justice Department did not respond to a request for comment. But legal experts said this speculation was illogical and far-fetched. Conspiracy is defined as an agreement between two or more people to commit a crime. An undercover federal agent or informant cannot be counted as a conspirator because those operatives do not actually intend to carry out the crime, the Congressional Research Service — the nonpartisan research agency for Congress — explains.

Jesse Norris, a criminal justice professor at the State University of New York at Fredonia who spent several years researching incidents of entrapment in terrorism prosecutions, said he had never come across a case where an F.B.I. informant was referred to as an “unindicted co-conspirator.”

“Legally, it wouldn’t make sense to call informants co-conspirators,” he said. “If they were authorized by the F.B.I. to participate in the conspiracy then they wouldn’t actually be conspirators, because they didn’t have the intent to commit a crime. Instead, they were pretending to commit a crime on the government’s behalf to catch real criminals.”

Ira P. Robbins, a law professor at American University who has written about unindicted co-conspirators, said calling an informant a co-conspirator would make no sense unless an F.B.I. agent had gone rogue.

“Even if that were true, to say that it’s true in one case so it’s true in every case — where’s the evidence?” he said. “Where are the facts?”

There are several reasons the government refers to someone as an “unindicted co-conspirator.” The co-conspirator may have cooperated with law enforcement and received a deal, or there may be insufficient evidence to bring charges against the individual.

In fact, it is the Justice Department’s policy to not name unindicted co-conspirators “in the absence of some significant justification.” (Former President Richard Nixon was famously named as an unindicted co-conspirator by a grand jury in the Watergate case, while former President Donald J. Trump was effectively labeled one in a campaign finance violations case.)

Mr. Carlson pointed to the indictment of Thomas Edward Caldwell, a 65-year-old Virginia resident whom charging documents described as an apparent leader of the far-right Oath Keepers group. Mr. Carlson claimed that unnamed persons mentioned in his indictment were “almost certainly working for the F.B.I.”

The indictment does mention multiple unnamed people. One of them — “Person 1” — is described in the charging documents as the leader of the Oath Keepers, widely known to be Stewart Rhodes. But there is no evidence Mr. Rhodes is an F.B.I. informant.

The charging documents describe “Person 2” taking selfies with Mr. Caldwell together at the Capitol. As the Washington Post reported, that person may refer to Mr. Caldwell’s wife. Mr. Caldwell posted a photo of himself and his wife at the Capitol on Jan. 6.

Mr. Carlson also noted that a plot to kidnap Gov. Gretchen Whitmer of Michigan last year involved F.B.I. operatives. That is true. But the operatives are not listed as “unindicted co-conspirators.” Rather, the criminal complaint refers to “confidential human sources” and “undercover employees.”

Similarly, in the Capitol riot cases, F.B.I. informants were described as “confidential source,” “confidential human source” or simply “informant,” while agents were described as “acting in an undercover capacity.”

And Mr. Carlson cited potential entrapment cases in terrorism prosecutions documented in the book “The Terror Factory” by the journalist Trevor Aaronson, adding, “That’s what we’re seeing now.”

This, too, is unlikely, experts said. In a recent study, Dr. Norris found that “right-wing cases have significantly fewer entrapment indicators” than those involving left-wing or jihadist terrorism cases.

“Not all undercover operations involve entrapment; probably, most do not,” Dr. Norris said.

Professor Robbins said that if F.B.I. agents were heavily involved in planning the attack, it would count as entrapment. But he said he was unaware of any Capitol riot participants raising entrapment as a defense.

“Tucker Carlson takes a great leap of faith here when he says that F.B.I. agents were involved, therefore they were operatives therefore they organized it,” he said. “There’s just no evidence of that.”

In fact, Mr. Eriksen has not been vaccinated, Inter Milan’s director told Gazzetta Dello Sport, an Italian sports publication.

That did not stop social media users from suggesting or claiming that he collapsed after receiving the vaccine. False rumors that he received the Pfizer vaccine or “got the jab” in May spread on Twitter and were reposted to Facebook in English, German, Italian, Greek, Dutch, Romanian, Portuguese, French, Polish and Arabic.

Some cited as their source of information a supposed radio interview on an Italian station with an Inter Milan doctor. But the radio station, Radio Sportiva, said on Twitter that it had not interviewed any Inter Milan medical staff members about Mr. Eriksen’s condition.

Others have pointed to an English translation of an Italian-language interview between Inter Milan’s club doctor and Gazetta Dello Sport as proof that Mr. Eriksen was vaccinated. The physician, Dr. Piero Volpi, told the sports publication in an interview published May 18 that all the players would be vaccinated at the start of the next championship. Dr. Volpi did not specify whether he was referring to Euro 2020 or the start of Serie A, Italy’s top soccer league, which restarts in August.

Mr. Eriksen is in stable condition at a hospital in Copenhagen. He released a statement on Monday in which he said he felt better.

It’s rare for athletes to collapse during games, but not unheard of. Fabrice Muamba, an English soccer player who is now retired, collapsed during a 2012 game between Bolton Wanderers and Tottenham Hotspur; his heart stopped beating for 78 minutes. Mr. Muamba told Sky Sports News that Mr. Eriksen “being alive is the best thing that can come out of Euro 2020.”

A 2017 study published in the Journal of the American College of Cardiology estimated an incidence rate of 1.04 sudden cardiac deaths per 100,000 person years among professional soccer players. This is relatively low, according to the study, but higher than the 0.72 rate among all sports-related incidents. A separate 2017 study in the New England Journal of Medicine identified soccer and race events as “the sports associated with the greatest number of cases of sudden cardiac arrest among competitive athletes.”

The Centers for Disease Control and Prevention is investigating reports that a small number of teenagers and young adults vaccinated against the coronavirus may have experienced heart problems. It will hold a meeting on Friday to discuss the cases.

Dr. Fauci “will not earn any royalties from its publication and was not paid” for the book, “Expect the Unexpected,” said Ann Day, a spokeswoman for National Geographic Books, its publisher. She said Dr. Fauci also would not earn anything for a related documentary. (Dr. Fauci did not respond to a request for comment.)

The book, which compiles interviews and speeches given by Dr. Fauci during his 37 years as the director of the National Institute of Allergy and Infectious Diseases, was taken off the websites because “it was prematurely posted for presale,” Ms. Day said. She added that proceeds would “go back to the National Geographic Society to fund work in the areas of science, exploration, conservation and education and to reinvest in content.”

In a statement, the national institute noted that the book had not been written by Dr. Fauci himself. The institute also confirmed that he would not earn any royalties from its publication.

The falsehood about the book and Dr. Fauci spread widely online. On May 31, the right-wing outlet The Daily Caller published an article about the book’s appearing for presale online. Some conservative Republicans, including Representatives Andy Biggs of Arizona and Dan Bishop of North Carolina, seized on the article and claimed without evidence that Dr. Fauci would be profiting from the book.

“His lockdown mandates destroyed livelihoods and threatened our children’s futures,” Mr. Bishop posted on Twitter on June 1. “Now he’ll be profiting nicely off it.” The post was liked and shared more than 2,700 times.

That same day, Newsweek and Fox News published articles highlighting the “backlash” that Dr. Fauci faced from right-wing commentators “for profiting from pandemic” after the announcement of his book. The articles did not mention that he would not make money from the book. They reached as many as 20.1 million people on Facebook, according to data from CrowdTangle, a social media analytics tool owned by the social network.

On June 2, a conservative outlet, Just the News, posted an article asserting that Dr. Fauci’s book had been “scrubbed” from Amazon and Barnes & Noble because of the backlash. The founder of the site, John Solomon — a Washington media personality who was instrumental in pushing falsehoods about the Bidens and Ukraine — tweeted the misleading article. So did the pro-Trump activist Jack Posobiec, who once promoted the false Pizzagate conspiracy.

“Books are removed from bn.com from time to time if the details are loaded incorrectly,” a Barnes & Noble spokeswoman said in a statement to The Times. “This book was not removed proactively by Barnes & Noble. We expect it will be available again shortly for purchase as soon as the publisher decides to list it.” Amazon did not comment.

Some articles on June 2, including on Fox News and The Daily Mail, included similar comments from National Geographic Books. But many outlets on the far right continued to push the version of events that the book had been “scrubbed” from online listings because of the backlash, without the updated information. The articles collected more than 32,000 likes and shares on Facebook and reached as many as six million people on Facebook, according to CrowdTangle data.

Days later, people like the Fox News host Sean Hannity and Representative Ronny Jackson, a Republican from Texas and former President Donald J. Trump’s onetime doctor, continued to push the false idea on Twitter.

“Anthony Fauci is set to make a fortune on his upcoming book; meanwhile our country continues to SUFFER from his ENDLESS non-scientific policies,” Mr. Jackson said on Twitter. His post collected nearly 4,000 likes, comments and shares.

Jacob Silver contributed research.

Since then, something interesting has happened: His claims of media distortion have not taken off among his conservatives supporters online, while the left has widely circulated and criticized his comments.

News stories and videos covering Mr. Flynn’s call for a coup gathered 675,000 likes and shares on Facebook and Twitter, according to a New York Times analysis. His denial, in comparison, collected only around 61,000 likes and shares on Facebook and Twitter.

Only a few big accounts on the right shared his denial in earnest, including Sid Miller, Texas’ agriculture commissioner and an outspoken supporter of Mr. Trump, whose post collected 68 likes and shares. Other shares came from right-wing partisan Facebook pages with names like Apostolic Conservatives Show and A Little to the Right.

By Wednesday, the chatter from right-wing accounts had died out, while many more left-leaning accounts kept up the discussion on his comments — but only to share their incredulity at Mr. Flynn’s original comments and his attempt to deny and reframe the call for a coup.

For example, the left-leaning Facebook pages Occupy Democrats, Being Liberal and Ridin’ With Biden were among the top sharers of Mr. Flynn’s comments.

“Should Mike Flynn get sent to prison for calling for a military coup against American democracy to violently reinstate Trump?” said one meme posted by Occupy Democrats on Tuesday. The one post alone collected more than 11,500 likes and shares.

Jacob Silver contributed reporting.

“Between late December of 2020 and last month, a total of 3,362 people apparently died after getting the Covid vaccine in the United States,” Mr. Carlson said on his show on Wednesday, citing the Centers for Disease Control and Prevention’s Vaccine Adverse Event Reporting System, or VAERS. “That’s an average of roughly 30 people every day. The actual number is almost certainly higher than that, perhaps vastly higher than that.”

But, as the federal Department of Health and Human Services notes in a disclaimer on its website, the database relies on self-reporting, and its reports may include unverified information.

“VAERS reports alone cannot be used to determine if a vaccine caused or contributed to an adverse event or illness,” the disclaimer reads. “The reports may contain information that is incomplete, inaccurate, coincidental or unverifiable. In large part, reports to VAERS are voluntary, which means they are subject to biases.”

When the C.D.C. examined VAERS reports on Covid-19 vaccines administered from Dec. 14 to May 3, it found 4,178 reports of deaths among people who had received one. The agency noted, however, that “a review of available clinical information, including death certificates, autopsy and medical records, has not established a causal link to Covid-19 vaccines.”

Reports have indicated a “plausible causal relationship” between Johnson & Johnson’s vaccine and a rare blood clotting disorder, according to the C.D.C. Three people who had received that vaccine and developed the blood clot illness died, according to a separate C.D.C. study.

Experts emphasized that the database was a useful tool to flag early warning signs for vaccine safety, but that it was not a replacement for studies on the effects of vaccines or actively monitoring side effects.

“It’s a big net to catch everything, not a way of evaluating what problems are actually caused by vaccines,” said Anna Kirkland, a professor at the University of Michigan and the author of a recent book on vaccine injury claims. “‘Died after getting a vaccine’ could mean you died in a car accident, you died of another disease you already had or anything else.”

Professor Kirkland also warned that lawyers and activists who wanted to make vaccines look more dangerous filed reports to the database and then cited those reports as evidence of danger.

Laura Scherer, a professor at the University of Colorado School of Medicine and the author of a study on the database and the HPV vaccine, called Mr. Carlson’s claim “a gross misuse of VAERS” and “fundamentally misleading.”

“VAERS reports accept a lot of noise in order to have a chance of being able to pick up on potentially important effects,” she said. “The key is that it is always necessary to follow up on those reported events with high-quality research.”

As an example of unsubstantiated suspicions captured in the database, Dr. Scherer cited a report she came across attributing a sudden death to the HPV vaccine three months after the vaccine was administered — an assertion, she said, that was extremely unlikely.

Mr. Carlson responded to criticisms on Thursday night by acknowledging that the database was unverified, but he maintained his suspicions over the vaccines, saying that “more deaths have been connected to the new Covid vaccines over the past four months than to all previous vaccines combined.”

That might be because of the enormous scale of the Covid-19 vaccination drive, an effort not seen in many decades.

“If you have millions of people getting a vaccine, and a lot of suspicion circulating about that vaccine, then you would expect to see more VAERS reports,” Dr. Scherer said. “But this does not mean that the vaccine caused any of these events, and an increase in reporting does not necessarily mean that this vaccine is more dangerous than other vaccines.”

In reality, it is impossible to experience any effects from being near a vaccinated person, because none of the vaccine ingredients are capable of leaving the body they were injected into.

The vaccines currently authorized for use in the United States instruct your cells to make a version of the spike protein found on the coronavirus, so your immune system can learn to recognize it. Different vaccines use different vehicles to deliver the instructions — for Moderna and Pfizer, messenger RNA, or mRNA; for Johnson & Johnson, an adenovirus genetically modified to be inactive and harmless — but the instructions are similar.

“It’s not like it’s a piece of the virus or it does things that the virus does — it’s just a protein that’s the same shape,” said Emily Martin, an infectious disease epidemiologist at the University of Michigan School of Public Health. “Transferring anything from the vaccine from one person to another is not possible. It’s just not biologically possible.”

Microorganisms spread from person to person by replicating. The vaccine ingredients and the protein can’t replicate, which means they can’t spread. They don’t even spread through your own body, much less to anybody else’s.

“They’re injected into your arm, and that’s where they stay,” Jennifer Nuzzo, an epidemiologist at Johns Hopkins, said of the vaccines. “mRNA is taken up by your muscle cells near the site of injection, the cells use it to make that protein, the immune system learns about the spike protein and gets rid of those cells. It’s not something that circulates.”

It’s also not something that sticks around. Messenger RNA is extremely fragile, which is one reason we’ve never had an mRNA-based vaccine before: It took a long time for scientists to figure out how to keep it intact for even the brief period needed to deliver its instructions. It disintegrates within a couple days of vaccination.

Vaccinated people can’t shed anything because “there’s nothing to be shedding,” said Dr. Céline Gounder, an infectious disease specialist at Bellevue Hospital Center and a member of President Biden’s transition advisory team on the coronavirus. “The people who shed virus are people who have Covid. So if you want to prevent yourself or others from shedding virus, the best way to do that is to get vaccinated so you don’t get Covid.”

This brings us to the reports of women having abnormal periods after being near vaccinated people. Because one person’s vaccine can’t affect anybody else, it is impossible for these two events to be connected. Many things, like stress and infections, can disrupt menstrual cycles.

The shedding claims are “a conspiracy that has been created to weaken trust in a series of vaccines that have been demonstrated in clinical trials to be safe and effective,” Dr. Christopher M. Zahn, vice president of practice activities at the American College of Obstetricians and Gynecologists, said in a statement. “Such conspiracies and false narratives are dangerous and have nothing to do with science.”

Some women have expressed a related concern that getting vaccinated themselves could affect their menstrual cycles. Unlike secondhand effects, this is theoretically possible, and research is ongoing — but anecdotal reports could be explained by other factors, and no study has found a connection between the vaccine and menstrual changes.

“There’s no evidence that the vaccine affects your menstrual cycle in any way,” Dr. Gounder said. “That’s like saying just because I got vaccinated today, we’re going to have a full moon tonight.”

“We know this trial has been painful for many people,” Monika Bickert, Facebook’s vice president of content policy, wrote in a blog post. “We want to strike the right balance between allowing people to speak about the trial and what the verdict means, while still doing our part to protect everyone’s safety.”

Facebook, which has long positioned itself as a site for free speech, has become increasingly proactive in policing content that might lead to real-world violence. The Silicon Valley company has been under fire for years over the way it has handled sensitive news events. That includes last year’s presidential election, when online misinformation about voter fraud galvanized supporters of former President Donald J. Trump. Believing the election to have been stolen from Mr. Trump, some supporters stormed the Capitol building on Jan. 6.

Leading up to the election, Facebook took steps to fight misinformation, foreign interference and voter suppression. The company displayed warnings on more than 150 million posts with election misinformation, removed more than 120,000 posts for violating its voter interference policies and took down 30 networks that posted false messages about the election.

But critics said Facebook and other social media platforms did not do enough. After the storming of the Capitol, the social network stopped Mr. Trump from being able to post on the site. The company’s independent oversight board is now debating whether the former president will be allowed back on Facebook and has said it plans to issue its decision “in the coming weeks,” without giving a definite date.

The death of Mr. Floyd, who was Black, led to a wave of Black Lives Matter protests across the nation last year. Mr. Chauvin, a former Minneapolis police officer who is white, faces charges of manslaughter, second-degree murder and third-degree murder for Mr. Floyd’s death. The trial began in late March. Mr. Chauvin did not testify.

Facebook said on Monday that it had determined that Minneapolis was, at least temporarily, “a high-risk location.” It said it would remove pages, groups, events and Instagram accounts that violated its violence and incitement policy; take down attacks against Mr. Chauvin and Mr. Floyd; and label misinformation and graphic content as sensitive.

The company did not have any further comment.

“As the trial comes to a close, we will continue doing our part to help people safely connect and share what they are experiencing,” Ms. Bickert said in the blog post.

Senator Tim Scott of South Carolina made a similar argument in a widely circulated post on Twitter.

But while the 15-day and 17-day numbers are accurate, the overall comparison is not. Here are four key differences between Colorado’s and Georgia’s systems.

• In Colorado, every registered voter receives a mail ballot by default.

  In Georgia, people who want to vote by mail must apply, and the new law more than halves the time they have to do that: Previously, they could apply as much as 180 days before an election, but now no more than 78 days before. Georgia also forbids officials to send voters an absentee ballot application unless they request it.

• In Colorado, eligible voters can register anytime, including on Election Day.

  In Georgia, the deadline to register to vote is a month before Election Day, and under the new law, the same deadline applies to any runoff — meaning if a Georgian is not registered by the deadline for the first election, they cannot subsequently register to vote in the runoff.

• In Colorado, only newly registered voters have to provide identification with their mail-in ballot; for subsequent elections, all that’s required is their signature. And contrary to Mr. Kemp’s statement, there is no photo requirement: Voters can use a birth certificate, a naturalization document, a Medicare or Medicaid card, a utility bill, a bank statement, a paycheck or another government document that shows their name and address.

  In Georgia, only photo identification is acceptable for regular mail-in ballots, and it has to be one of six specific types. The requirement will apply to everyone who votes by mail, not just to newly registered voters as in Colorado.

• In Colorado, there were 368 ballot drop boxes last year across the state’s 64 counties, not just in government buildings but also at schools, parks, libraries, businesses and more. Boxes were open 24 hours a day.

  In Georgia, the new law requires at least one drop box in each of the 159 counties. (Mr. Kemp and other officials note that before the pandemic, Georgia didn’t have drop boxes at all.) The boxes will be only at registrars’ and absentee ballot clerks’ offices or inside early-voting sites, and open during limited hours.

In 2020, Colorado had the second-highest turnout rate in the country: 76.4 percent of eligible voters, behind only Minnesota, according to data compiled by the United States Elections Project. Georgia was 26th, with a turnout rate of 67.7 percent of eligible voters.

In an effort to demonstrate its effectiveness in finding and removing rule-breaking videos, YouTube on Tuesday disclosed a new metric: the Violative View Rate. It is the percentage of total views on YouTube that come from videos that do not meet its guidelines before the videos are removed.

In a blog post, YouTube said violative videos had accounted for 0.16 percent to 0.18 percent of all views on the platform in the fourth quarter of 2020. Or, put another way, out of every 10,000 views on YouTube, 16 to 18 were for content that broke YouTube’s rules and was eventually removed.

“We’ve made a ton of progress, and it’s a very, very low number, but of course we want it to be lower,” said Jennifer O’Connor, a director at YouTube’s trust and safety team.

The company said its violative view rate had improved from three years earlier: 0.63 percent to 0.72 percent in the fourth quarter of 2017.

YouTube said it was not disclosing the total number of times that problematic videos had been watched before they were removed. That reluctance highlights the challenges facing platforms, like YouTube and Facebook, that rely on user-generated content. Even if YouTube makes progress in catching and removing banned content — computers detect 94 percent of problematic videos before they are even viewed, the company said — total views remain an eye-popping figure because the platform is so big.

YouTube decided to disclose a percentage instead of a total number because it helps contextualize how meaningful the problematic content is to the overall platform, Ms. O’Connor said.

YouTube released the metric, which the company has tracked for years and expects to fluctuate over time, as part of a quarterly report that outlines how it is enforcing its guidelines. In the report, YouTube did offer totals for the number of objectionable videos (83 million) and comments (seven billion) that it had removed since 2018.

While YouTube points to such reports as a form of accountability, the underlying data is based on YouTube’s own rulings for which videos violate its guidelines. If YouTube finds fewer videos to be violative — and therefore removes fewer of them — the percentage of violative video views may decrease. And none of the data is subject to an independent audit, although the company did not rule that out in the future.

“We’re starting by simply publishing these numbers, and we make a lot of data available,” Ms. O’Connor said. “But I wouldn’t take that off the table just yet.”

YouTube also said it was counting views liberally. For example, a view counts even if the user stopped watching before reaching the objectionable part of the video, the company said.

They told themselves that “the storm” — the day of reckoning, in QAnon lore, when the global cabal would be brought to justice — would take place on March 4. That is the day that U.S. presidents were inaugurated until 1933, when the 20th Amendment was ratified and the date was moved to January. Some QAnon believers thought that it would be the day that Mr. Trump would make a triumphal return as the nation’s legitimate president, based on their false interpretation of an obscure 19th century law.

Law enforcement agencies, worried about a repeat of the Jan. 6 riot at the Capitol, took note of QAnon’s revised deadline and prepared for the worst. The Department of Homeland Security and the F.B.I. sent intelligence bulletins to local police departments warning that domestic extremist groups had “discussed plans to take control of the U.S. Capitol and remove Democratic lawmakers.” And the House of Representatives canceled plans to be in session on Thursday, after the Capitol Police warned of a possible QAnon-inspired plot to stage a second assault on the Capitol.

But the Capitol was quiet on Thursday, and QAnon supporters did not erupt in violence. Mr. Trump remains a former president, and no mass arrests of pedophiles have been made.

Even before their latest prophecy failed, QAnon believers were divided about the movement’s future. Some movement influencers who originally promoted the March 4 conspiracy theory had walked back their support for it in recent days, insisting it was a “false flag” operation staged by antifa or other left-wing extremists in order to make QAnon look bad.

On Thursday, as it became clear that no storm was underway, some QAnon believers defiantly maintained that there was still time for Mr. Trump to stage a coup and take office. One Telegram channel devoted to QAnon chatter lit up with false claims that Bill Gates, Dr. Anthony S. Fauci, Representative Alexandria Ocasio-Cortez and other prominent officials had been arrested or executed for treason already, and that “doubles and A.I. clones” had been activated to preserve the illusion that they were still alive.

But other believers contested those claims and appeared resigned to postponing their day of reckoning yet again.

“It may not happen today,” one poster on a QAnon message board wrote. “But when it happens, everyone will see it! As Q predicted. And yes, it will be much much sooner than in four years. We are talking about days (weeks max).”

Twitter will notify people when it applies a label to one of their tweets, and repeated violations of the Covid-19 policy will result in stricter enforcement, the company said. Two or three strikes result in a 12-hour account lock, while four strikes is a seven-day account lock. After five strikes, Twitter said, the company will permanently suspend the account. (Twitter allows users to submit appeals if accounts are locked or suspended in error.)

The company said it was making these changes to encourage healthy conversation on the platform and help people find reliable information. Since introducing its Covid-19 guidance last March, Twitter said, it had removed more than 8,400 tweets and notified 11.5 million accounts of possible violations worldwide.

Online video channels with QAnon content generated more than one billion views in 2020, with 910 million on YouTube alone, up 38 percent from 2019, the report said. When YouTube began to directly crack down on people posting the QAnon conspiracy theories in October, the largest channels moved to smaller platforms, BitChute and Rumble.

Sam Clark, a co-founder of Pendulum, said the research “indicates that moderation done by YouTube has not been enough to stop the growth of overall viewership of this content.”

The report demonstrated the critical role that YouTube, a subsidiary of Google, played in helping to move QAnon from a fringe phenomenon into the mainstream with violent offline consequences.

In a recent national poll, 17 percent of respondents said they believed in one of the core tenets of QAnon — that a group of devil-worshiping elites who run a child sex ring are trying to control politics and the media. And QAnon believers were involved in the deadly Capitol riot in January as well as other offline violence.

“While we welcome more peer-reviewed research, our data contradicts Pendulum’s findings, and just over the past months alone, we have terminated many prominent QAnon channels and removed thousands of videos for violating our policies,” Farshad Shadloo, a YouTube spokesman, said in a statement.

Mr. Shadloo said Pendulum’s sampling was not comprehensive and did not accurately reflect what was popular or what was watched on YouTube. He added that a number of factors could drive an increase in views, including a sudden increase in media coverage, attention from public figures and sharing outside YouTube.

After YouTube changed its algorithm in January 2019, it said views from recommendations among a set of pro-QAnon channels fell more than 80 percent. The updated policy in October said YouTube would no longer allow “content that targets an individual or group with conspiracy theories that have been used to justify real-world violence.”

Pendulum said YouTube had removed 91,000 videos from 285 of the largest QAnon channels and removed about half of those channels altogether. YouTube has not disclosed the full impact of its policy change, but said the majority of its prominent QAnon channels had been terminated.

But YouTube’s actions did not stop the biggest creators of QAnon content. They simply moved to smaller video platforms with less restrictive moderation policies, such as BitChute and Rumble.

When YouTube took action in October, the number of daily views of QAnon channels on all three platforms fell to 1.3 million from 2.7 million. As followers of those top creators moved to the smaller platforms, daily views rose again, to 2.2 million in December.

And after the attack on the Capitol, QAnon channels had their highest-viewed month ever — topping their previous record by 30 percent, with most of the views on BitChute and Rumble.

Pendulum labeled a channel a QAnon channel when 30 percent of more of its most-viewed videos discussed the conspiracy theory in a supportive way or indicated that the content creator was a believer.

Even so, dozens of prominent anti-vaccine activists remained active on Facebook and Instagram on Thursday, according to an analysis by The New York Times. Some of the accounts had large followings, including the Instagram account for Children’s Health Defense, the nonprofit organization that Mr. Kennedy runs, which has over 172,000 followers.

A search for the word “vaccine” on Instagram on Thursday showed that four of the top 10 accounts took strong anti-vaccine positions. A search for the hashtag #vaccine got three results, one of which was #vaccinetruthadvocate, a term that anti-vaccine activists often use to spread their message. The hashtag was appended to more than 12,000 posts.

“This is going to take some time, however, but we are working to address what you raise,” a Facebook spokeswoman said in a statement.

Researchers who study misinformation said Facebook continued to struggle to contain Covid-19 falsehoods.

“Months after they promised to crack down on Covid misinformation, we reported hundreds of posts containing dangerous misinformation to Facebook, but just one in 10 of those posts were removed,” said Imran Ahmed, chief executive of the nonprofit Center for Countering Digital Hate. “Millions of people are being fed dangerous lies which lead them to doubt government guidance on Covid and on vaccines, prolonging the pandemic. These lies cost lives.”

Here’s a look at some of the prominent accounts still spreading anti-vaccine misinformation on Instagram.

Children’s Health Defense

The nonprofit regularly promotes seminars and webinars with vaccine skeptics through its Instagram account, and posts misleading accounts of death and injury associated with the Covid vaccine. Many of its posts receive tens of thousands of likes. The organization did not return a request for comment.

Erin Elizabeth

An author and public speaker who has campaigned for years against vaccines, Ms. Elizabeth has over 122,000 Instagram followers on her Health Nut News page and 23,700 on another page she runs. She regularly shares content that argues against “mandatory vaccination.” She did not return a request for comment.

Shiva Ayyadurai

Mr. Ayyudurai, an Indian-American politician, has over 299,000 followers on Instagram. He has spread the false claim that Covid-19 can be treated with vitamin C. He has also accused the “deep state,” or the conspiracy theory that a secret cabal runs the government, of spreading Covid-19. He did not return a request for comment.