Dr. Paul Malarik, a retired psychiatrist, now spends about 50 hours a month helping to administer Covid-19 vaccines at pop-up clinics near his home in San Luis Obispo, California. So he’s particularly troubled when he logs onto Doximity, a site used by doctors, and reads anti-vaccine comments.

“You rarely get to the level of microchips in vaccines, but a lot of this stuff is pretty close to it,” said Malarik, who volunteers his time to mix vaccines, put shots in arms and educate the public. “They’re actively working against us.”…

Malarik read directly from several comments posted by people with the initials M.D. or D.O., which indicates doctor of osteopathic medicine, after their names. There’s no anonymity on the site, so everyone is identified. In the posts, they refer to the vaccines as experimental, unproven or deadly and occasionally write “Fauxi” when talking about Dr. Anthony Fauci, the White House chief medical advisor.