Misinformation messengers pivot from election fraud to peddling vaccine conspiracy theories.

Sidney Powell, a lawyer who was part of President Trump’s legal team, spread a conspiracy theory last month about election fraud. For days, she claimed that she would “release the Kraken” by showing voluminous evidence that Mr. Trump had won the election by a landslide.

But after her assertions were widely derided and failed to gain legal traction, Ms. Powell started talking about a new topic. On Dec. 4, she posted a link on Twitter with misinformation that said that the population would be split into the vaccinated and the unvaccinated and that “big government” could surveil those who were unvaccinated.

“NO WAY #America,” Ms. Powell wrote in the tweet, which collected 22,600 shares and 51,000 likes. “This is more authoritarian communist control imported straight from #China.” She then tagged Mr. Trump and the former national security adviser Michael T. Flynn — both of whom she had represented — and other prominent right-wing figures to highlight the post.

Ms. Powell’s changing tune was part of a broader shift in online misinformation. As Mr. Trump’s challenges to the election’s results have been knocked down and the Electoral College has affirmed President-elect Joseph R. Biden Jr.’s win, voter fraud misinformation has subsided. Instead, peddlers of online falsehoods are ramping up lies about the Covid-19 vaccines, which were administered to Americans for the first time this week.

Apart from Ms. Powell, others who have spread political misinformation such as Representative-elect Marjorie Taylor Greene, a Republican of Georgia, as well as far-right websites like ZeroHedge, have begun pushing false vaccine narratives, researchers said.

Their efforts have been amplified by a robust network of anti-vaccination activists like Robert F. Kennedy Jr. on platforms including Facebook, YouTube and Twitter.

Among their misleading notions is the idea that the vaccines are delivered with a microchip or bar code to keep track of people, as well as a lie that the vaccines will hurt everyone’s health (the vaccines from Pfizer and Moderna have been proved to be more than 94 percent effective in trials, with minimal side effects). Falsehoods about Bill Gates, the Microsoft co-founder and philanthropist who supports vaccines, have also increased, with rumors that he is responsible for the coronavirus and that he stands to profit from a vaccine, according to data from the media insights company Zignal Labs.

The shift shows how political misinformation purveyors are hopping from topic to topic to maintain attention and influence, said Melissa Ryan, chief executive of Card Strategies, a consulting firm that researches disinformation.

It is “an easy pivot,” she said. “Disinformation about vaccines and the pandemic have long been staples of the pro-Trump disinformation playbook.”