More than 500,000 children tested positive for Covid-19 in 3 weeks. Experts say school mask mandates are needed

US states that saw some of the country's worst Covid-19 case rates over the past week also reported the highest number of new vaccinations per capita, data published Thursday by the US Centers for Disease Control and Prevention shows. Tennessee, which reported the country's worst Covid-19 cases rate, had the sixth-best rate of new vaccinations per capita in the US over the past week. The state's hospitals are 'under increasing strain from the highly contagious Delta variant,' Tennessee's health department wrote on Twitter Thursday, adding in a statement that the strain was continuing to fuel an increase in infections.