Pinterest has stopped returning results for searches related to vaccinations, a drastic step the social-media company said is aimed at curbing the spread of misinformation but one that demonstrates the power of tech companies to censor discussion of hot-button issues.

Most shared images on Pinterest relating to vaccination cautioned against it, contradicting established medical guidelines and research showing that vaccines are safe, Pinterest said. The image-searching platform tried to remove the antivaccination content, a Pinterest spokeswoman said, but has been unable to remove it completely.

Pinterest described the search ban—which the company hasn’t previously publicly discussed but which went into effect late last year—as a temporary but necessary measure until it can develop better strategies to sift through what it calls “polluted” content. The company made a similar decision last year to block searches for dubious cancer therapies.

Users can still pin vaccine-related images to their online boards, which could lead to suggestions for similar content, but the posts no longer show up in searches. “It’s better not to serve those results than to lead people down what is like a recommendation rabbit hole,” said Ifeoma Ozoma, Pinterest’s public policy and social impact manager.

The technology industry is grappling with the thorny issue of how and when to take responsibility for information on its platforms. Companies including Twitter Inc. and Facebook Inc. have begun to police hate speech, violence, terrorism-recruitment campaigns and sexual harassment on their services, shutting down millions of accounts. But those actions also have sparked counter-complaints about everything from political bias and censorship to a lack of transparency in the process.