An investigation by The New York Times — involving scores of interviews as well as a review of scholarly papers, news reports, and Russian documents, tweets and TV shows — found that Mr. Putin has spread misinformation on issues of personal health for more than a decade.

The Russian president has waged his long campaign by means of open media, secretive trolls and shadowy blogs that regularly cast American health officials as patronizing frauds.

The K.G.B. campaign — which cast the deadly virus that causes AIDS as a racial weapon developed by the American military to kill black citizens — was wildly successful.

Within Russia, Mr. Putin has been a staunch proponent of vaccines. At the same time, Mr. Putin has worked hard to encourage Americans to see vaccinations as dangerous and federal health officials as malevolent