Users can still post vaccination material on their boards, a spokeswoman said -- you just can't set out to find it unless you visit specific users and check the suggestions for related boards. Most of the material on the subject pushed anti-vaccination views, the spokeswoman added.

Pinterest has also been blocking some cancer-related searches, accounts and content over questionable cancer therapies.

The acknowledgment of search bans is a response to growing attention to the vaccination issue. A county in Washington state has been struggling with a measles outbreak that some attribute to parents believing discredited claims that vaccinations cause autism. Other internet giants have faced pressure to clamp down on these falsehoods as well. Facebook recently said it might stop recommendations of anti-vaccination content, while Google largely intends to rely on information panels that counter web and YouTube search results promoting anti-vaccine beliefs. It's just that Pinterest's response is the most drastic -- it would rather stop vaccination talk altogether than risk contributing to the problem.