OKLAHOMA CITY — By the summer of 2021, Phil Maytubby, deputy CEO of the health department here, was concerned to see the numbers of people getting vaccinated against covid-19 slipping after an initially robust response. With doubt, fear, and misinformation running rampant nationwide — both online and offline — he knew the agency needed to rethink its messaging strategy. So, the health department conducted something called an online “sentiment search,” which gauges how certain words are perceived on social media. The tool found that many people in Oklahoma City didn’t like the word “vaccinate” — a term featured prominently in the health department’s marketing campaign. “If you don’t know how…