Why is Warren County the most-vaccinated county in our region? Warren County is on a roll. About 43% of people who live there have started their COVID-19 vaccination, according to data collected by the Ohio Department of Health â a higher percentage than the statewide average or any of the eight counties that surround Warren, including Hamilton. and last updated 2021-04-28 20:16:12-04 Warren County is on a roll. About 43% of people who live there have started their COVID-19 vaccination, according to data collected by the Ohio Department of Health â a higher percentage than the statewide average or any of the eight counties that surround Warren, including Hamilton.