President Biden blasted Facebook and other social-media companies over the spread of misinformation around Covid-19 vaccines on their platforms.

“They’re killing people,” Mr. Biden said Friday afternoon in response to a question about his message to companies like Facebook about misinformation. “The only pandemic we have is among the unvaccinated. And they’re killing people.”

The Biden administration this week has raised concerns about misinformation, with the pace of vaccinations down in the U.S. and the highly transmissible Delta variant spreading. Experts say the vaccines are highly effective against Covid-19. U.S. health regulators have warned that the Johnson & Johnson vaccine is linked to a very small incidence of cases of a rare neurological disorder associated with other shots.

Misinformation being circulated on Facebook Inc. makes various claims, including that the vaccine can lead to infertility, according to the White House. The Centers for Disease Control and Prevention says there is no evidence that the Covid-19 vaccines cause female or male fertility problems.

Facebook spokesman Kevin McAlister said that Mr. Biden’s claim wasn’t supported by facts and that more than 3.3 million Americans have used a Facebook tool to find out where to get a vaccine. “The facts show that Facebook is helping save lives. Period,” he said.

Facebook said earlier Friday that it had “removed more than 18 million pieces of COVID misinformation, removed accounts that repeatedly break these rules, and connected more than 2 billion people to reliable information about COVID-19 and COVID vaccines across our apps.”

The Biden administration has said social-media companies aren’t doing enough. It has cited research indicating a significant amount of false information comes from 12 social-media users. Administration officials are also flagging problematic posts to social-media companies, White House press secretary Jen Psaki said, and they have asked Facebook to remove posts more quickly.

“We’re dealing with a life or death issue here,” Ms. Psaki said Friday. “And so everybody has a role to play in making sure there’s accurate information.” She said that it was up to Facebook to decide what steps to take but that it was clear they could do more.

Surgeon General Vivek Murthy issued an advisory Thursday warning against health misinformation. “Modern technology companies have enabled misinformation to poison our information environment, with little accountability to their users,” he said.

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Some Republicans have criticized the White House’s handling of the issue. GOP Sen. Josh Hawley of Missouri wrote in a letter to Facebook dated Thursday that the administration flagging posts it viewed as spreading misinformation amounted to directing the company “to police speech.” He asked Facebook to detail any social-media posts it deleted at the administration’s request.

Joan Donovan, director of research at Harvard University’s Shorenstein Center on Media, Politics and Public Policy, said the spread of vaccine misinformation is a deeply rooted problem on social media dating back more than a decade.

The false narratives that Covid-19 vaccines result in death and that the U.S. government is mandating vaccines more than doubled across the major social-media platforms within the past three months, according to Zignal Labs Inc. Others include claims that vaccines are really microchips and that vaccines change people’s DNA, the media-analytics firm said.

The White House is also enlisting celebrities and other influential people to urge Americans to get vaccinated against Covid-19. This week, pop star Olivia Rodrigo visited Mr. Biden and made videos for her social-media network, which the White House said has 28 million followers.

—Alex Leary contributed to this article.

Write to Tarini Parti at Tarini.Parti@wsj.com and Sarah E. Needleman at sarah.needleman@wsj.com