But first we're focusing on the race to vaccinate children as a path toward herd immunity. As COVID-19 vaccinations progress, one key demographic remains largely unvaccinated: children. Globally, and in Memphis, kids make up about a quarter of the population, our Laura Testino and Corrine Kennedy report in this story. Until that key population is inoculated, reaching herd immunity — already a fluid and elusive target — will be almost impossible, medical experts said. Getting safe and effective vaccines for younger age groups will be essential to ending the pandemic and returning to any sense of normal, they reported. MPD director search delayed; Mike Ryall named interim director